FZ750 Maintenance Advice
David Higgins
Hi,
Well I've just bought an '85 FZ750 as my first big bike. Previously I
owned a CB250RS which gave me much pleasure to learn on. However the
CB was a simple thing to maintain, I just made sure the chain was oiled
and changed the oil once in a while. Now I've got this huge 4 cyclinder
thing with no manual and a very unhelpful local motorbike store.
I'm after some advice on the basic maintenance needed and the intervals
at which they should be undertaken. The bike is used for some commuting
and some touring, and the occasional thrash.
Has anyone had any experiance with this bike, if so I'd like to hear
your thoughts on it.
David
--
"I wouldn't trust no words written on no piece of paper by no Dickinson
out in the town of Machine."
David Higgins
Triple G Corporation (Special Projects Group)
Joshua Pryor
David Higgins (dave....@tripleg.com.au) wrote:
:
: Well I've just bought an '85 FZ750 as my first big bike. Previously I
: owned a CB250RS which gave me much pleasure to learn on. However the
: CB was a simple thing to maintain, I just made sure the chain was oiled
: and changed the oil once in a while. Now I've got this huge 4 cyclinder
: thing with no manual and a very unhelpful local motorbike store.
Hey nice choice!
best you can do is change the oil regularly, say every 3-6 months
and keep the chain lubed
Have fun!
--
------------------------------------------------
Josh Pryor c960...@alinga.newcastle.edu.au
DON'T MAKE ME WAIT
--------------------240Z----FJ1100----A1200T----
Bob Gross
David Higgins wrote:
>
> Hi,
>
> Well I've just bought an '85 FZ750 as my first big bike. Previously I
> owned a CB250RS which gave me much pleasure to learn on. However the
> CB was a simple thing to maintain, I just made sure the chain was oiled
> and changed the oil once in a while. Now I've got this huge 4 cyclinder
> thing with no manual and a very unhelpful local motorbike store.
>
> at which they should be undertaken. The bike is used for some commuting
> and some touring, and the occasional thrash.
>
> Has anyone had any experiance with this bike, if so I'd like to hear
> your thoughts on it.
>
> David
> --
> "I wouldn't trust no words written on no piece of paper by no Dickinson
> out in the town of Machine."
>
> David Higgins
> Triple G Corporation (Special Projects Group)
wealth of info about your bike (far more than the official factory
job). I got one for my Yamaha RZ(RD in UK)250R and it was worth every
cent. If you are unable to order one through your bike shop you can
order on-line from Crooks Suzuki at >
http://www.ellisweb.com/crooks-suzuki/haynes.html
Hope this helps
Roadrace24
Some friends of mine raced one a few years ago. After a 24 hour
endurance, the valves didn't even need to be adjusted. We changed the oil
and tires and went to the next race with never a mechanical problem.
I would suggest you do the normal maintenance and enjoy a great bike!
Sean P. Clarke
WERA PN #24 84 FJ1100
91 GSX-R1100 - Will it ever run?
93 KAF300 - Mule
Gavern Spencer
Good to hear about the FZ
The best thing that I've found is to take the recommended Yamaha service
intervals and halve them. (Oils, filters chain lube etc depending upon
usage i.e. daily/ weekly, sports/touring/commuting.
Personally (no car, to/from work, hard riding & LOTS of touring) I used:
Chain lube - 500 km or after heavy rain or a wash (with a check for wear)
Gear oil - 3000 - 5000 km with a new oil filter every 2nd oil change
Fork oil & Brake fluid every 12 to 18 months
Shims - 20,000 km
Having said that, believe it or not the recommended interval for valve
clearance/shims service of 42,00 km works, although I only let it go for
that long once (BUT did change oils etc...). How do I know that this
works? 200,000 km including a trip form Perth to Cape Tribulation and all
round the east.
Just traded to a YZF1000 partly because of the above.
One final word - When the time comes to replace chain & sprokets, go for
OE Yamaha Sprokets and the BEST O-ring chain (better than OE if possible)
you can afford (about $300 to $350 a set last time). They may cost nearly
twice as much as cheap & nasties but they last at least 3 to 4 times
longer.....
Good luck and Good Riding (& you'll get plenty of that on the FZ)
David Higgins
Hi Gavern,
Thanks for the advice, and thanks to all the other who replied with
advice on the
FZ maintenance. I'm really enjoying having a big bike (well big
compared to my old
CB250RS) and I'm very pleased with the FZ.
Another question: How many other FZ owners have a full fairing, one
person to reply to my
maintenance post said that the '85 didn't come with the full fairing but
after market ones
could be bought. Judging by the way my underbelly of the fairing is
attached it looks aftermarket.
Gavern Spencer wrote:
>
> Good to hear about the FZ
>
> The best thing that I've found is to take the recommended Yamaha service
> intervals and halve them. (Oils, filters chain lube etc depending upon
> usage i.e. daily/ weekly, sports/touring/commuting.
>
> Personally (no car, to/from work, hard riding & LOTS of touring) I used:
> Chain lube - 500 km or after heavy rain or a wash (with a check for wear)
> Gear oil - 3000 - 5000 km with a new oil filter every 2nd oil change
> Fork oil & Brake fluid every 12 to 18 months
> Shims - 20,000 km
>
Thanks. Will do.
[snip]
> Just traded to a YZF1000 partly because of the above.
>
Mmmm....Yes Please.
[snip]
> Good luck and Good Riding (& you'll get plenty of that on the FZ)
Thanks, you too.
Joshua Pryor
David Higgins (dave....@tripleg.com.au) wrote:
:
: Another question: How many other FZ owners have a full fairing, one
: person to reply to my
: maintenance post said that the '85 didn't come with the full fairing but
: after market ones
: could be bought. Judging by the way my underbelly of the fairing is
: attached it looks aftermarket.
I think the fairing was introduced in around 1987, if you frame is painted
to look like alloy, then it is the newer model, with the standard full
fairing.
Barry Maguire
David Higgins <dave....@tripleg.com.au> wrote:
>The >other thing is that the power down low in the rev's is non-existant.
>When taking off from lights it bogs down if I don't get the revs
>up before releasing the clutch. Is this common for the FZ, my local
>motorbike store had a look at it and said that it was normal and
>that you had to ride high in the revs to avoid it. It has a 4-2-1
>exhaust which the store says the bike hasn't be re-jetted for (there
>is a dip in power around 4,500RPM) could this also be causing the lack
>of low down power.
>PS. I am by no means an amateur mechanic, so any advice is apprecated
>David Higgins
>Triple G Corporation (Special Projects Group)
David,
I have a 1987 model FZ (FZ750T) with an aftermarket 4-2-1 exhaust.
Likewise, I haven't had the carburettors re-jetted, and there is a
marked dip in power from 4000-4500 rpm. 100 kmh touring is right in
this range - bit of a bastard really. However, this doesn't have any
effect on low revs power. I can bog the bike when I take off, but I
think this is just me getting slack or not concentrating sometimes.
Joshua's comments about the fairing and frame paint I think are right.
I have copies of the AMCN and Two Wheels articles from 1985 when the
FZ was released, if you are interested (email barr...@werple.net.au).
That was the S model, I think.
Andrew Smale
Yamaha FZ750T
David Higgins
Hi
Joshua Pryor wrote:
>
> David Higgins (dave....@tripleg.com.au) wrote:
> :
> : Another question: How many other FZ owners have a full fairing,
[snip]
>
> I think the fairing was introduced in around 1987, if you frame is painted
> to look like alloy, then it is the newer model, with the standard full
> fairing.
Nope, it's a black painted frame so I guess it is an '85ish bike. The
Tony Whiteley
David Higgins <dave....@tripleg.com.au> wrote in article
<32D57CA8...@tripleg.com.au>...
> Nope, it's a black painted frame so I guess it is an '85ish bike. The
> other thing
> is that the power down low in the rev's is non-existant. When taking
> off from lights
> it bogs down if I don't get the revs up before releasing the clutch. Is
> this common
> for the FZ, my local motorbike store had a look at it and said that it
> was normal and
> that you had to ride high in the revs to avoid it.
The pipes on my '85 FZ rusted out in '89 and I changed them for a set of
Staintune pipes. No rejetting was required and the power was just like the
Yamaha pipes ie. starting at idle. If you don't mind taking a long time to
do it the bike will pull smoothly from idle in top gear on a flat road! I
had a minor drop on a dirt road a few years ago that put a dent in one
muffler and decided to buy a 4 into 1 pipe. Can't remember who the company
was but it was in Melbourne somewhere. From the time I put it on there was
a BIG flat spot around 3-4,000 rpm. I tried everything I could think of
with the carbs but couldn't get rid of it. I rang the manufacturer and they
told me that FZ's were like that and they raced with their pipes. They
weren't interested in hearing that standard FZ's don't have a flat spot and
didn't want to help me. Ultimately I sent the damaged Staintune pipe back
to Staintune and had it repaired. Good as new and no too expensive. The 4
into 1 got dumped into the garbage.
BTW the 4 into 1 gave lousy fuel economy at any revs.
Gavern Spencer
Low bottom end grunt???? The FZ was well known for the abundance of power
down low...
(But then again, my previous was an RZ500 with as much bottom end as an
anorexic supermodel......)
As for bogging down mid-range, you'll have to do a little tweaking to the
jets and needles to correct that one.
When I bought the FZ second hand it had some nonedescript gold slip-ons. I
think the jets then were 112 (8 years back mind you...) Standard I believe
are 105?. Big jump.
I replaced that exhaust with a Supertrapp 4-1 (stainless headres,
aluminium muffler) and put a DynoJet kit in the carbies (c/w 4 sets of
main jets, needles & diaphragm lift springs). Your local dealer should
exchange the main jets for about $5-$10 per set. At this set-up I think I
settled for 108 jets, with a little adjustment to the needles which had
grooves to accomodate 4 major height settings plus thin washers for
incremental heights.
Now here's where Supertrapp comes in. The end of the muffler is blanked
off with dispersion discs placed between the muffler and the end blank and
the exhaust gasses exit radially through the discs. This in effect
increases the backpressure at the headers and overall length of exhaust,
somewhat similar the the old RZ (2 stroke) I suppose. The real beauty of
the Supertrapp is that the number of dispersion rings can be added to or
subtracted from to decrease/increase the backpressure/exhaust length
depending upon POWER vs FUEL CONSUMPTION vs DECIBELS needed (or wanted?)
So in effect, after settling on approximate carby settings, the Supertrapp
could be used for fine tuning.
COST - around $900 (1989) for the stainless pipes, aluminium muffler about
12 dozen rings and the DynoJet kit. This was ex-USA back then mind you and
there was only one other that I knew of in Australia at the time. Now that
there's a few more around and even an importer I believe it may be
cheaper.
BTW, next time you see (or hear - they generally sound like a big-bike,
although more tinny) an RX3, 4 or 5 check out it's exhaust. 2 will give
you 1 that there's a Supertrapp on it's bum.
In the end, it was all worth it. I had as many comments about the looks of
the thing ("But there's no hole for the exhaust to come out..") as I did
for the sound.
The moral of this story:
If your exhaust is simply 4-2 slipons, leave the carbies alone.
With a 4-2-1 at least try a few jet sizes (not too big) and move the
needle a notch either way. With a 4-1-1 rejet the carbies and/or use a
DynoJet kit. (~$100 kit to ~$350 fitted)
Best of luck. It's not as hard as it sounds. The only pain is having to
remove the whole carby assembly each time to get to the needles.
Sam Michaelson
David Higgins wrote:
The
> other thing
> is that the power down low in the rev's is non-existant. When taking
> off from lights
> it bogs down if I don't get the revs up before releasing the clutch. Is
> this common
> for the FZ, my local motorbike store had a look at it and said that it
> was normal and
> that you had to ride high in the revs to avoid it. It has a 4-2-1
> exhaust which the store
> says the bike hasn't be re-jetted for (there is a dip in power around
> 4,500RPM) could this
> also be causing the lack of low down power.
>
> PS. I am by no means an amateur mechanic, so any advice is apprecated
>
> David Higgins
> Triple G Corporation (Special Projects Group)
G'day again Dave
Okay, well, to a 'by no means amateur mechanic' from someone who can't
work out which end of the angle grinder plugs into the wall, but for what
it's worth, the jetting (or apparent lack of it) may well be the problem.
My FZ ('85 model) was fitted with a Megacycle (4into1 from memory, with
Zen baffles, hee hee hee, did he sound mean or what!!!), but hadn't been
rejetted, when I bought him, resulting in a similar problem to yours
(bogged down easily, loss of bottom end power, very mediocre fuel
economy, etc etc etc). Went up 2 sizes (to 110, I think, but this was
several years ago, he's long since gone to the big wreckers in the sky)
and minimised the bog down problem. Also made a vast improvement in the
power down low, to my embarrassment. I'd had the bike for a couple of
weeks, then he went back for his new jets and a service - "Be careful",
sez Mr Mechanic, "It'll cut in a bit differently now, so take it easy on
the way home". So off I go, and pull up at the first set of lights,
half-noticing the plod on the other side of the road. The light went
green, I opened the throttle and let out the clutch, and Thorfin the FZ
gave this unholy howl and shot through the intersection of the back
wheel. Fortunately for me, my face was completely white, so when Mr Plod
pursued me and pulled me over, he believed me when I said in a quavering
voice, "But officer, he's never done that before!"
Sam (Thorfin's Mummy) - just for today, disowning my naughty GSX
David Higgins
Sam Michaelson wrote:
[snip]
> FZs are wonderful
> FZs are nice
> We love/d our FZs
> But I crashed mine (twice)
>
> FZs are quick and
> Will go like a shot
> But if they fall on you
> They hurt quite a lot
>
> My FZ was white
> The decals were red
> Then a car squashed him
> And now he's just dead
>
> FZs are noisy
> FZs are fun
> If I win Tattslotto
> I'll buy myself one
>
> Okay, okay, I won't give up my day job just yet, sheesh, everyone's a
> critic.....
Nah... Byron was an amatuer compared to you ;)
You could make a song out of it, sung to the tune of my 4-2-1 slip-on.
(But no-one would hear you due to the unholy din)
[snip]
> Well, yes, but if the bastard ever tank slaps on you, you'll know all
> about it. That was how I sustained my very first Fair Dinkum Nasty Bike
> Injury, shredded half the muscles on my left shoulder by hanging onto a
> full-lock tank-slap at around 150 k's on my FZ (I was too terrified to
> jump off, and I was worried that if I did he might fall down on the wrong
> side and ruin the pipe).
Well alright it's time to reveal my total newbieness and lack of
motorcycling friends and relatives. I can guess, but what exactly
is tank slapping. As you can probably guess I've spent my first few
months
on the FZ getting used to it. I've done the rear wheel steering thing
through corners and have had the pleasure of experiancing wheel spin in
the
first 4 gear changes due to a nice greasy wet road, but I don't think
I've
ever come close to tank slapping. So what happens and why and what do
you
do if it does and how can we bring world peace and equality?
David
Damian Carvolth
In article <32D9A63B...@tripleg.com.au>, David Higgins <dave....@tripleg.com.au> says:
>
>Sam Michaelson wrote:
>[snip]
>first 4 gear changes due to a nice greasy wet road, but I don't think
>I've
>ever come close to tank slapping. So what happens and why and what do
>you
>do if it does and how can we bring world peace and equality?
>
>David
Tank slappers are when the front end goes into resonance and shakes
back and forth between steering locks uncontrollably. The name comes
from your hands (if they are still on the bars) slapping each side
of the tank, and doing much damage to hands and tank...
Frankly I'm shocked the japs still make bikes that do this. I was shocked
when a friend mentioned how his RGV does it occasionally. Put me off buying
one straight away...
People keep telling me the japanese have learned to make bikes that handle.
I want to believe it but it's hard when you hear stuff like this..
Someone tell me I've got it all wrong.
Damian Carvolth
"I'm just a startled bunny in the headlights of life", L.J. Young
dam...@dem.csiro.au
Sam Michaelson
David Higgins wrote:
Hey, are you the Dave who came of about 12 months ago and buggered his
wrist and it wouldn't heal and you had to have surgery etc etc etc???
>
> Hi Gavern,
>
> Thanks for the advice, and thanks to all the other who replied with
> advice on the
> FZ maintenance. I'm really enjoying having a big bike (well big
> compared to my old
> CB250RS) and I'm very pleased with the FZ.
>
> Another question: How many other FZ owners have a full fairing, one
> person to reply to my
> maintenance post said that the '85 didn't come with the full fairing but
> after market ones
> could be bought. Judging by the way my underbelly of the fairing is
> attached it looks aftermarket.
That's right, the '85 model (FZ750N) was the half-fairing one, after that
they came out with a full fairing (numbers prefixed with IFU. Yeah, I
still remember my FZ's number, IFU000204)
My old FZ was a half-fairing job, and for aesthetic reasons only I liked
the half-fairing better than the full one - I dunno, there was just
something nice about being able to see the engine. It was also great on
winter, because at the lights I could just lean down a bit, and tuck my
hands under the fairing and in behind the engine, thereby warming my
gloves up and keeping my fingers toasty up to the next intersection.
Have fun with your FZ (erk, and your 16" front wheel..... :-)
Sam (Thorfin's Mummy)
- yeah, I know, but mention of FZs always makes me nostalgic
Fitz
David Higgins <dave....@tripleg.com.au> wrote:
>Well alright it's time to reveal my total newbieness and lack of
>motorcycling friends and relatives. I can guess, but what exactly
>is tank slapping.
"Tank slapping" is a front-wheel oscillation which causes the steering
head to turn back and forth rapidly. At its worst, your handlebars
will be going from extreme left to extreme right, while your bowels
empty all through your nice new leathers and your vocal cords rupture
from excessive screaming.
It can be caused by a number of things, among which are crappy
steering-head bearings, uneven front tire wear, and Bad Fairies.
I've heard various strategies for getting out of them, but since they
all seem to contradict each other and I've never actually had to try
any of them, I won't bother detailing them here.
=========================================================
And remember, kiddies, never procrastinate today when you
can procrastinate tomorrow.
=========================================================
Fitz of Fitz Hall
fi...@tpnet.co.nz
Sam Michaelson
David Higgins wrote:
>
> Sam Michaelson wrote:
> >
> > David Higgins wrote:
snip snip
FZs are wonderful
FZs are nice
We love/d our FZs
But I crashed mine (twice)
FZs are quick and
Will go like a shot
But if they fall on you
They hurt quite a lot
My FZ was white
The decals were red
Then a car squashed him
And now he's just dead
FZs are noisy
FZs are fun
If I win Tattslotto
I'll buy myself one
Okay, okay, I won't give up my day job just yet, sheesh, everyone's a
critic.....
> > Have fun with your FZ (erk, and your 16" front wheel..... :-)
> Already have and will continue to do so. What's the deal with the 16"
> front
> wheel. I read the FZ was the only bike to actually make good use of it.
Well, yes, but if the bastard ever tank slaps on you, you'll know all
about it. That was how I sustained my very first Fair Dinkum Nasty Bike
Injury, shredded half the muscles on my left shoulder by hanging onto a
full-lock tank-slap at around 150 k's on my FZ (I was too terrified to
jump off, and I was worried that if I did he might fall down on the wrong
side and ruin the pipe).
Sam (Thorfin's Mummy) - still haven't forgiven the GSX, even if it's her
birthday.
David Higgins
Sam Michaelson wrote:
>
> David Higgins wrote:
>
> wrist and it wouldn't heal and you had to have surgery etc etc etc???
[SNIP]
> My old FZ was a half-fairing job, and for aesthetic reasons only I liked
> the half-fairing better than the full one - I dunno, there was just
> something nice about being able to see the engine. It was also great on
> winter, because at the lights I could just lean down a bit, and tuck my
> hands under the fairing and in behind the engine, thereby warming my
> gloves up and keeping my fingers toasty up to the next intersection.
I must admit that I like a good naked bike too, but the full fairing
looks
pretty good too. I guess the advantage is God forbid I drop it I have
the
option of leaving it half faired, and won't loose anything in the looks
dept.
> Have fun with your FZ (erk, and your 16" front wheel..... :-)
Already have and will continue to do so. What's the deal with the 16"
front
wheel. I read the FZ was the only bike to actually make good use of it.
--
"I wouldn't trust no words written on no piece of paper by no Dickinson
out in the town of Machine."
David Higgins (FZ750)
the demon..
In article <32DA6A...@dsto.defence.gov.au>, Sam Michaelson <sam.mic...@dsto.defence.gov.au> wrote:
(snip)
>> Hi Gavern,
>>
>> Thanks for the advice, and thanks to all the other who replied with
>> advice on the
>> FZ maintenance. I'm really enjoying having a big bike (well big
>> compared to my old
>> CB250RS) and I'm very pleased with the FZ.
>>
>> Another question: How many other FZ owners have a full fairing, one
>> person to reply to my
>> maintenance post said that the '85 didn't come with the full fairing but
>> after market ones
>> could be bought. Judging by the way my underbelly of the fairing is
>> attached it looks aftermarket.
>
>
>That's right, the '85 model (FZ750N) was the half-fairing one, after that
>they came out with a full fairing (numbers prefixed with IFU. Yeah, I
>still remember my FZ's number, IFU000204)
>
>the half-fairing better than the full one - I dunno, there was just
>something nice about being able to see the engine. It was also great on
>winter, because at the lights I could just lean down a bit, and tuck my
>hands under the fairing and in behind the engine, thereby warming my
>gloves up and keeping my fingers toasty up to the next intersection.
>
>
>
>- yeah, I know, but mention of FZs always makes me nostalgic
My '85 FZ has full fairing (Matich race model - Number 002). I am unsure as to
whether the Matich originally came with the full fairing or bikini but the
three bikes I know of all have full fairing. Any further info on the Matich FZ
would be greatly appreciated.
the demon..
Sam Michaelson
David Higgins wrote:
munchymunchy...poetry and critique removed munchymunchy <burrrrp>
>
> Well alright it's time to reveal my total newbieness and lack of
> motorcycling friends and relatives. I can guess, but what exactly
> is tank slapping.
Do not mourn your ignorance of this phenomenon (doo doooooo de doo doo).
A tank-slapper is when the handlebars start to wobble backwards and
forwards quickly, while the bike is moving. If you're lucky, you'll be
going in a straight line and not moving too fast.
>As you can probably guess I've spent my first few
> months
> on the FZ getting used to it. I've done the rear wheel steering thing
> through corners and have had the pleasure of experiancing wheel spin in
> the
> first 4 gear changes due to a nice greasy wet road, but I don't think
> I've
> ever come close to tank slapping. So what happens
See above
>and why
Er, um, good question, I'm glad you asked, well done that man..... I
haven't the slightest idea, although I suspect things like knackered head
stem bearings and unbalanced wheels don't help. I'm sure that one of our
More Physically Inclined Netter Nutters Out There can explain the physics
of it. However, I can tell you that hitting a corrugated dirt road at
speed on an FZ has the potential to cause a reeeeely good one. Ouch,
pass me that cortisone injection, nurse.....
I'm given to believe that a smaller front wheel, all other things being
equal, can be more likely to cause a tank slapper, but anyone who knows
better feel free to shoot me down on that. Rooth (I think) has written a
bit in the February Two Wheels about and article about the physics of the
'quickness' of steering of a smaller front wheel. 'Gyroscopic effect',
stuff like that, don't ask me, I dropped physics after first year, I'll
get the magazine and have a proper look. Come on, boffins, educate us
iggerant ijits.
>and what do
> you
> do if it does
I suppose the best thing to do is to back off gently from doing whatever
it was that you were doing that precipitated it, and hope it goes away.
In the case of a really nasty one, you can opt to jump off the bike
(which may damage you) or hang onto it (which may damage you, people have
broken arms hanging on), however, since we are all bike people here and
we love our children, I'm sure that you'd stay on board and hang on,
taking any damage necessary to protect your fairing.
>and how can we bring world peace and equality?
I would start by making it illegal to instruct anyone in any religion
until they were 18 - 21, of an age where they were able to think for
themselves, but that's probably not relevant to this newsgroup.
Say hello to your FZ for me. Does he/she have a name yet?
Sam (Boadicea's Mummy) - yes, Boadicea has been forgiven, even if she did
boil her battery on her birthday.
Graham Byrnes
In article <5bclka$c...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
Carvolth) wrote:
>
> Frankly I'm shocked the japs still make bikes that do this. I was shocked
> when a friend mentioned how his RGV does it occasionally. Put me off buying
> one straight away...
Tank-slappers are a concommitant of faster cornering bikes. My GSXR750T
did it (even with a steering damper). John Kocinski's Ducati was close
to it a lot of the time. Mark Ferrari's 916 did a monster the *whole*
length of the straight at Phillip Is, bringing the laconic response
from another Ducati rider watching:
"Yeah, they do that. You have to go 18" left of the lights over the
line or they slap real bad."
Watch some video of Corser at Assen... big shakes through the whole
bike while driving out of the chicane.
If you rake out the front end, the bike is more stable but it just won't
turn fast enough at speed. Old Jap bikes used to have flexible frames
which led them to slap even with slow steering geometry. Now the frames
and weight distribution are much better, but the steering has been sped
up to take advantage.
If it's any consolation, my GSXR would only slap at low speed if you clipped
a bump while accelerating hard enough for the front to be lifting, or at
high speed at full power on a ridge or rise that made the front light.
The one at the start/finish line at PI does it nicely. I followed Mark
Ferrari at Stars of Tomorrow and the 916 did big wobbles out of Siberia,
over the crest and into Hayshed every lap... until he lost the front
and threw it away. (Not that I was anywhere near following him then).
You actually get used to the smaller ones, although it is tiring to hang
on and bring them back. If they get to the stage of your feet blowing
off the pegs (like MF's 200+km/h effort) it's change of underwear time,
but I don't recall anyone crashing from a big slapper.
Graham
PS You don't need a 16" wheel to slap...
Ted Palmer
David Higgins <dave....@tripleg.com.au> wrote:
[...]
>Already have and will continue to do so. What's the deal with the 16"
>front
>wheel. I read the FZ was the only bike to actually make good use of it.
You must have read that in a Yammie brochure.
Before the FZ came the Honda CBX750F with its 16" front.
Two Wheels reckoned that the Honda had excellent high speed
stability. My experience at Phillip Island verifies that.
The best thing to do with 16" fronts is to stick to the factory tyre
size and use a good tyre like the Metzeler ME33 Laser or Comp K.
Mister_T
"Like a bolt of lightning from the sky comes Honda's CBX750, the
fastest, brawniest 750 we've ever tested." Two Wheels, April 1984
--
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\
| RC17 KLR600 Coherent 4.2.10 OS/2 2.11 Roces BCN |
| FreeBSD 2.1.5-R te...@replicant.apana.org.au |
\|_________________________________________________________________|
Helen Hayden
Fitz says...
>
>It can be caused by a number of things, among which are crappy
>steering-head bearings, uneven front tire wear, and Bad Fairies.
>
off my steering head bearings in the middle of the night. Good thing that the
White Knight of motorcycle mechanics came over my house and fixed it up before
the little GSXR booted me off in a tank slapper. (Thanks Damian!)
Helen
GSXR400
Ted Palmer
fi...@tpnet.co.nz (Fitz) wrote:
[...]
>It can be caused by a number of things, among which are crappy
>steering-head bearings, uneven front tire wear, and Bad Fairies.
Oi! You left one out: trying to get off a wet tram track on a mighty
KLR600.
I did big slappers twice at the same spot on Toorak Road in wet
conditions on the mighty KLR. A 21" front wheel is no guarantee
it won't happen.
For the curious:
The is a place on Toorak Road (West?) where a tramline does
a 90 deg bend from a side road on to Toorak Road.
I was heading up from the St Kilda Rd end of Toorak Rd, where
there are no tram lines, then suddenly there are some.
Each time I managed to cross the intersection and ride straight
along to the wet tram line. The front wheel gets out off the tram line
quite easily, but the rear is a bit reluctant. So I ended up cruising
along at about 60kmh with the front wheel about 1.5 feet away
from the tram line, and the back wheel right on it.
The bike was some noticable angle from the direction of travel.
Eventually, the rear tyre gripped and sent the bike into a big
slapper. Slappers are bad enough with little clipon bars, but
try it sometime with bars a yard wide...
Each time, the mighty KLR kept me from injury, and I take a
different route in the wet.
Normally, in the dry. you just ignore tram lines while riding the KLR.
You can brake on them, ride with your legs on the radiator air
scoops etc etc but in the wet it's a whole different kettle of
friction coefficients.
Mister_T
"On the road, however, the KLR gets revenge by holding the top
honours in outright speed."
Two Wheels April 1985 4-way traillie comparo
Damian Carvolth
In article <G.Byrnes-140...@graham-byrnes.maths.latrobe.edu.au>, G.By...@latrobe.edu.au (Graham Byrnes) says:
>
>In article <5bclka$c...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
>Carvolth) wrote:
snip..
For what it's worth I never intended this to look like a flame..
>If you rake out the front end, the bike is more stable but it just won't
>turn fast enough at speed. Old Jap bikes used to have flexible frames
>which led them to slap even with slow steering geometry. Now the frames
>and weight distribution are much better, but the steering has been sped
>up to take advantage.
Yaeh I don't buy that excuse. Your right in as far as it goes but on the
road you simply don't need that. A slight increase in rake would cure the
instability and the bike wouldn't lose any speed on road. In fact I'm told
someone is marketing an aftermarket frame for the fireblade with slower
steering. They are patching one prob and making another..
Personally I suspect the factories have it all wrong. I used to work in
product development for an automotive concern and I know how it's done. Mostly
by chance and politics, and marketing of course. Technical engineering comes
last.
Remember the 16" wheel farce in the 80's ? In the late 70's people got the
idea that fat tyres were good cos the crossplys had a contact patch the size
of a maggot and would slide over less than perfect surfaces.
Trouble is the fatter tyres made teh bikes steer slower, so people fitted 16"
wheels. Then radials came out and naturally they made them fat cos they look
horney and bigger is better right ? Trouble is radials have a bigger contact
patch due to less distortion from centrifugal force, so they don't need to be
5" wide...
Anyway because they finally woke up and realised 16" wheels were a stupid
idea they went to 17" (because 18" are obviously low tech). So now you
have bikes that steer like a mach truck so you gotta reduce rake to 23
degrees and hang off like buggery to get them to steer.
Ducati have gone severely backwards in motorcycle design. The lap times
for the new 748 aren't that wonderful compared to the SS's of 20 years ago,
and what little improvment there is is power related.
Don;t get me wrong. Radials are good things but I suspect road bikes with
narrower radials and slower steering would be just as quick and much easier
to ride.
Or maybe I'm just stuck in the 70's...
>PS You don't need a 16" wheel to slap...
I know. I'm told it's almost impossible to get an SB6 to slap, but the source
of that info was dubious, and I can't ride that quick. I'm waiting with baited
breath for the VDue. It it's stable then my point is made. If it ain't then
I'll shut up.
Howeaver I'd never ride a bike that handles like that.
Ever got the 450 to do that Zebee ?
Graham Byrnes
In article <5bhaot$r...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
Carvolth) wrote:
>
> For what it's worth I never intended this to look like a flame..
Neither did I :-)
>
> Yaeh I don't buy that excuse. Your right in as far as it goes but on the
> road you simply don't need that. A slight increase in rake would cure the
> instability and the bike wouldn't lose any speed on road.
Well, I jacked up the back of the GSXR and liked it better on the road...
<shrug>
In fact I'm told
> someone is marketing an aftermarket frame for the fireblade with slower
> steering. They are patching one prob and making another..
The fireblade has problems other than it's geometry (which is no faster
than a ZX-6R, for eg). Its forks and a too high C of G, for eg.
> Remember the 16" wheel farce in the 80's ?
Reality check. My VF750F had a 110/90-16 on it stock. It *never* slapped
on me, even on dirt. Put a 120/80 Pirelli on, still no prob.
My previous bike was a Ducati GT-500S. That did more and more vicious
tank slappers than anything else I've ever owned (MX bikes included). It had
a narrow section 18" front and slow geometry. Oh, I had to hang off
to buggery to turn it, too.
Moreover, a 110/90 has a bag height of 99mm. A CBR-600 has a 120/60-17,
with a bag height of 72mm, on a rim 12.7mm bigger in radius, which makes
it: 14mm *smaller* than the infamous 16" wheel tyre combo's of the 80's...
The CBR also has much faster steering and more power, but they are quite
stable (until the racers get them and drop the front and raise the rear).
Something to do with a better frame, weight distribution and suspension,
I suspect...
Oh, another snippet. The RGV has a 25 degree rake. Like a ZZR-11...
>
> Ducati have gone severely backwards in motorcycle design. The lap times
> for the new 748 aren't that wonderful compared to the SS's of 20 years ago,
> and what little improvment there is is power related.
With who riding? The Euro SS 748s are bloody fast...
> Don;t get me wrong. Radials are good things but I suspect road bikes with
> narrower radials and slower steering would be just as quick and much easier
> to ride.
Don't know. I remember the same GT500 happily pushing the front across the road
at fairly sedate speed, with state of the art tyres for its day.
Graham
Helen Hayden
In article <5bharm$r...@news.cat.csiro.au>, D.Car...@dem.csiro.au says...
>
>You gotta stop this Helen, your embarrassing me..
>
>Head bearings loosen without the help of fairies. It's normal wear.
>
Embarrassing you is heaps of fun, Damian!!
Hel
Zebee Johnstone
On 15 Jan 1997 01:09:49 GMT, Damian Carvolth <D.Car...@dem.csiro.au> wrote:
>
>
>Howeaver I'd never ride a bike that handles like that.
>
>Ever got the 450 to do that Zebee ?
>
Nope. I've had it hard over on ripply corners and heard the
motor go raaw-raaw-raaw as the back wheel pattered over the
bumps, and I've had the front end feel a bit waggly but its
never tankslapped.
Its a very old-fashioned bike of course - big narrow wheels and
all the weight over the back. No idea how it would go with
someone who could ride fast :)
I did get into a tankslapper on my GPz250 - hammering hard in a
straight line when it hit a bump and got airborne. Bars walloped
side to side, we landed, it gave one more enormous shake and
then continued on as though nothing had happened. I pulled over,
stopped, got off, and shook more than it had :)
--
Zebee Johnstone (ze...@zip.com.au), proud holder of
aus.motorcycles Poser Permit #1.
"Motorcycles are like peanuts... who can stop at just one?"
Barry Maguire
barr...@werple.mira.net.au (Barry Maguire) wrote:
>David Higgins <dave....@tripleg.com.au> wrote:
[snip]
>David,
>I have a 1987 model FZ (FZ750T) with an aftermarket 4-2-1 exhaust.
>Likewise, I haven't had the carburettors re-jetted, and there is a
>marked dip in power from 4000-4500 rpm. 100 kmh touring is right in
>this range - bit of a bastard really. However, this doesn't have any
>effect on low revs power. I can bog the bike when I take off, but I
>think this is just me getting slack or not concentrating sometimes.
[snip]
I just had a quote of ~$360 from the Yamaha dealer to re-jet my bike.
This includes labour and parts, but is not firm. At the moment, I'm
not going to get it done until I have more money in the bank! The
bike is quite enjoyable the way it is, but I can't help thinking of
what it may be like if this work is done. (Images of Sam's wheelie
from the lights in front of Mr. Plod, etc).
Andrew Smale
Yamaha FZ750T
Damian Carvolth
>I'll look out for the Bad Fairies. They must have been the ones that loosened
>off my steering head bearings in the middle of the night. Good thing that the
>White Knight of motorcycle mechanics came over my house and fixed it up before
>the little GSXR booted me off in a tank slapper. (Thanks Damian!)
You gotta stop this Helen, your embarrassing me..
Head bearings loosen without the help of fairies. It's normal wear.
Damian Carvolth
In article <G.Byrnes-150...@graham-byrnes.maths.latrobe.edu.au>, G.By...@latrobe.edu.au (Graham Byrnes) says:
>
>In article <5bhaot$r...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
>Carvolth) wrote:
>>
>> For what it's worth I never intended this to look like a flame..
>
>Neither did I :-)
I'm glad.
>> Remember the 16" wheel farce in the 80's ?
>
>Reality check. My VF750F had a 110/90-16 on it stock. It *never* slapped
>on me, even on dirt. Put a 120/80 Pirelli on, still no prob.
>My previous bike was a Ducati GT-500S. That did more and more vicious
>tank slappers than anything else I've ever owned (MX bikes included). It had
>a narrow section 18" front and slow geometry. Oh, I had to hang off
>to buggery to turn it, too.
What's a GT500S ? Are you referring to a sport desmo ? If it's
a parrallel twin I'm surprised as they were sucessfully raced in teh late
70's and early 80's. Their handling is spoken about with reverance, and that
in teh bevel era.
>Moreover, a 110/90 has a bag height of 99mm. A CBR-600 has a 120/60-17,
>with a bag height of 72mm, on a rim 12.7mm bigger in radius, which makes
>it: 14mm *smaller* than the infamous 16" wheel tyre combo's of the 80's...
>The CBR also has much faster steering and more power, but they are quite
>stable (until the racers get them and drop the front and raise the rear).
It has nothing to do with rolling radius. It has to do with centrifugal
force. This and only this is what keeps you up on a bike. This is determined
not only by the mass of the wheel but ho far from the axel the mass lives.
>Something to do with a better frame, weight distribution and suspension,
>I suspect...
Yeah I've heard this about biasing the weight to the front wheel, what is
it 55%. Dunno...the physics of cornering make me wonder about that. But I've
not done an experiment.
>Oh, another snippet. The RGV has a 25 degree rake. Like a ZZR-11...
More than the 23 of the blade and less than the 29 of an SS. So you reckon
they slap cos they aren't set up right ?
>> Ducati have gone severely backwards in motorcycle design. The lap times
>> for the new 748 aren't that wonderful compared to the SS's of 20 years ago,
>> and what little improvment there is is power related.
>
>With who riding? The Euro SS 748s are bloody fast...
I'll have to look up some lap times on courses that haven't been modded in
the last 20 years. Do they race them on the Isl of Mann ?
>> Don;t get me wrong. Radials are good things but I suspect road bikes with
>> narrower radials and slower steering would be just as quick and much easier
>> to ride.
>
>Don't know. I remember the same GT500 happily pushing the front across the road
>at fairly sedate speed, with state of the art tyres for its day.
Crossplys. When was that then ? what year ?
Gee this is the most interesting thread I've seen on aus.moto in months :)
Damian Carvolth
In article <5bhqha$umj$1...@nargun.cc.uq.oz.au>, H.Ha...@tpp.uq.edu.au (Helen Hayden) says:
>
>In article <5bharm$r...@news.cat.csiro.au>, D.Car...@dem.csiro.au says...
>>
>>
>>Head bearings loosen without the help of fairies. It's normal wear.
>>
I'm blushing...bad girl Helen.
John McGhie
David Higgins <dave....@tripleg.com.au> wrote:
>Well alright it's time to reveal my total newbieness and lack of
>motorcycling friends and relatives. I can guess, but what exactly
>is tank slapping. As you can probably guess I've spent my first few
>months
>on the FZ getting used to it. I've done the rear wheel steering thing
>through corners and have had the pleasure of experiancing wheel spin in
>the
>first 4 gear changes due to a nice greasy wet road, but I don't think
>I've
>ever come close to tank slapping. So what happens and why and what do
>you
>do if it does and how can we bring world peace and equality?
David:
The previous poster was right: if you *ever* get into a tank-slapper, you
*will* know all about it :-)
A modern motorcycle chassis fitted with the correct tyres at even near to the
correct pressures is actually immune from this horrible disease, so I wouldn't
lie awake at nights worrying about them...
But for those of us old enough to have started on sundry British machinery
(like my Norton Dominator) the scenario goes something like this...
The front wheel loses traction momentarily and then bites again.
This sets up a violent twitching of the handlebars. The frame and the forks
act as springs, storing the energy and causing a violent oscilation of the
handlebars.
The reason they're called "tank slappers" is that the handlebar motion is so
violent that the steering hammers from lock to lock bouncing off the full-lock
stops (and usually, crushing your thumbs against the sides of the tank).
Normally if you simply pull in the clutch and wait, a modern motorcycle will
(eventually) calm itself down. Usually, you get two or three quick
oscillations and then it settles down and you can pull over and change your
underwear.
However, if the chassis is really poorly designed or the tyres are in a really
bad state, or you are riding an elderly British motorcycle, the bike is
capable of an advanced form of tank-slapper called a Death Wobble.
The Death Wobble is the same thing, and has the same cause (frame and fork
flex) but it starts by itself at a certain (high) speed. In the old days,
there was nothing you could do about a death wobble other than try to chose a
soft spot to land.
These days, brakes are much more powerful. If you get time to think, and
haven't fallen off already, grab the front brake and lock it up. Then
straighten the handlebars and release the brake. The *theory* is that
skidding the front tyre damps the oscilation and the bike will then proceed
straight ahead.
In practice, it gives you something to do while you are falling off. If you
live, check your tyre profiles and pressures afterward.
Bikes that have been modified to quicken the steering can sometimes suffer
from this, if the modifier didn't really know what they were doing. In the
old days, the suburbs would waft with the smell of pimply youths taking a gas
axe to their motorcycle frames to "improve" the handling. In these days of
alloy, heat-treated frames, it's pretty rare to find a frame that has been
modified.
*Every* frame flexes a little bit, and will oscilate (with the engine mounted)
at a particular frequency. *Every* front fork flexes a bit, and will also
oscilate at a given freqency. The amount of trail in the front geometry sets
the rate at which the front wheel attempts to centre itself after being
knocked off line. Tank slapping actually has nothing to do with the wheel
size, it's the amount of trail that determines what happens. (A small size
front wheel reduces steering effort and raises the frequency at which it will
oscilate, but whether this results in tank slapping depends upon all the rest
of the variables.)
If the two freqeuncies of oscilation match (or are harmonics of) the frequency
at which the trail centres the front wheel... look for a soft spot to land.
To measure the trail, draw a line through the steering head and the front axle
and extend it down to the ground. Now measure from the point of intersection
on the ground back to the centre of the point where the tyre contacts the
ground. Typically, the tyre contacts the road about five centimetres behind
the line.
Sports bikes (e.g. the FZ) have less trail for quicker steering and lower
steering effort. Touring bikes have longer trail for greater stability.
Hope this helps.
John McGhie
jmc...@magna.com.au
GSX-1100G - Nothing exceeds like GRUNT!
peter....@dsto.defence.gov.au
In article <5bclka$c...@news.cat.csiro.au> D.Car...@dem.csiro.au (Damian Carvolth) writes:
>In article <32D9A63B...@tripleg.com.au>, David Higgins <dave....@tripleg.com.au> says:
>
>
>Tank slappers are when the front end goes into resonance and shakes
>back and forth between steering locks uncontrollably. The name comes
>from your hands (if they are still on the bars) slapping each side
>of the tank, and doing much damage to hands and tank...
>
Fit a hydraulic steering damper, then adjust it so you can just barely
feel that it's there under normal riding. Over-rapid handlebar movement
will be severely restricted, however and a tank-slapper can never happen.
They cost between $100 and $300 and take less than half an hour to fit.
Now if I could just figure out where to put the one I have onto Hagar so
that it won't get broken next time I throw him away!!!!
============================================================
_--_|\ peter....@dsto.defence.gov.au (Business)
/ DSTO \ NBC Defence, Ship Structure & Materials Div.
\_.--._/ Defence Science & Technology Organisation
v Fax : 61-3-9626 8410 Voice: 61-3-9626 8411
Peter Sanders
sand...@melbpc.org.au (Private)
Voice: 61-3-9337-6612
Fantic 305, Hagar the Honda XR600RN
============================================================
Sam Michaelson
Damian Carvolth wrote:
>
> In article <G.Byrnes-150...@graham-byrnes.maths.latrobe.edu.au>, G.By...@latrobe.edu.au (Graham Byrnes) says:
munchmunchmunch
> What's a GT500S ? Are you referring to a sport desmo ? If it's
> a parrallel twin I'm surprised as they were sucessfully raced in teh late
> 70's and early 80's. Their handling is spoken about with reverance, and that
> in teh bevel era.
>
> >Moreover, a 110/90 has a bag height of 99mm. A CBR-600 has a 120/60-17,
> >with a bag height of 72mm, on a rim 12.7mm bigger in radius, which makes
> >it: 14mm *smaller* than the infamous 16" wheel tyre combo's of the 80's...
> >The CBR also has much faster steering and more power, but they are quite
> >stable (until the racers get them and drop the front and raise the rear).
>
> It has nothing to do with rolling radius. It has to do with centrifugal
> force. This and only this is what keeps you up on a bike. This is determined
> not only by the mass of the wheel but ho far from the axel the mass lives.
GOOOONNNNNNNNGGGGGGGGGGG!!!!!!!
Hang on, hang on, it's the old 'centrifugal force' chestnut - wasn't it Prof
Julius Sumner-Miller who first said of centrifugal force that "There aint no
such animal"? Come on, Dr Graham, say something, I dropped physics after
first year.....
Sam (Boadicea's Mummy)
Laurence Crew
Personally, I like tank-slappers. They add to the excitement of any
ride! Most of the bikes I have ridden (with the exception of my BMW R65)
have tank-slapped at some stage. The ideal conditions are accelerating
out of a corner on a bumpy road - the combination of cornering, the lack
of weight on the front wheel, and the road surface can inspire the most
stable bike to shake it's headstock. The Nasho is a prime breeding
ground for tank slappers.
So long as you keep thinking, "I am going to live", you usually do - I
have discovered from much experience that these things rarely get too
far out of control. Steering dampers - baah.
A few choice tank-slapping bikes:
* KR-250 - With the legendary 16" front wheel. Small vibes frequently,
with the occasional arm-ripper. The bike handles very nicely, mind you,
even with the 16" front. Also looks horny due to the 18" rear and the
resultant forward rake. Shame the motor kept blowing up.
* RG-250 - Small vibrations on nearly every corner. Just to make sure
you know you're turning. Also exhibited some lovely death wobbles (near
highside) when sliding the rear.
* Honda Spada. Only when pushed (high speed sweepers) - but tends to
slap once hard left, once hard right, then back on track. Buzz! (Thanks
for the ride, Cath!)
* GSX-250 (breadbox tank model) - OK, this could have been something to
do with the buckled front wheel - but slapped with the best of them.
* AG-80 (green frame) Even though this thing has 18" wheels on both ends
and is generally completely stable, I've had a few nice ones with the
power on. The bike is so light that any loss of traction / control can
be corrected without falling off.
* BMW R-65 - So far, predictable. Does have one concession of a high
speed (high speed for an R65 means 140+) weave from the rear, which can
be almost as much fun as a slapper. I'll have to keep working on the
front ..
- Laurence
> >Sam Michaelson wrote:
> >[snip]
>
> >first 4 gear changes due to a nice greasy wet road, but I don't think
> >I've
> >ever come close to tank slapping. So what happens and why and what do
> >you
> >do if it does and how can we bring world peace and equality?
> >
> >David
>
Silk - Young
Snip Snip Snip......
Can anyone fill me in on the rest of this discussion? (Please Email). I'm
rather interested in the mechanical aspects.
For my part, the radius and the mass of the wheel affect the lateral
stability of the bike, (ie leaning left and right) which is more or less
centrifugal force. Small front wheels however provide quicker steering
(due to lower centrifugal force) which is great on the race track (race
tracks have very smooth surfaces) but on the road (not so smooth at the
best of times) they tend to turn small bumps into big bumps which has an
adverse effect on the handling of the bike.
That is, conditions being ideal the small front wheel is better, however,
the conditions are not ideal, so err on the conservative side.
(I'd prefer the larger front wheel for practicality on the road.)
If anyone is interested in handling aspects (and discussion) please email
me and I will try to dig out the actual formula..........
Regards,
Scott Young.
Ian Drysdale
peter....@dsto.defence.gov.au wrote:
>
> In article <5bclka$c...@news.cat.csiro.au> D.Car...@dem.csiro.au (Damian Carvolth) writes:
> >In article <32D9A63B...@tripleg.com.au>, David Higgins <dave....@tripleg.com.au> says:
> >
> [chop]
> >
> >back and forth between steering locks uncontrollably. The name comes
> >from your hands (if they are still on the bars) slapping each side
> >of the tank, and doing much damage to hands and tank...
> >
>
> Fit a hydraulic steering damper, then adjust it so you can just barely
> feel that it's there under normal riding. Over-rapid handlebar movement
> will be severely restricted, however and a tank-slapper can never happen.
> They cost between $100 and $300 and take less than half an hour to fit.
>
> Now if I could just figure out where to put the one I have onto Hagar so
> that it won't get broken next time I throw him away!!!!
>
> ============================================================
> _--_|\ peter....@dsto.defence.gov.au (Business)
> / DSTO \ NBC Defence, Ship Structure & Materials Div.
> \_.--._/ Defence Science & Technology Organisation
> v Fax : 61-3-9626 8410 Voice: 61-3-9626 8411
> Peter Sanders
> sand...@melbpc.org.au (Private)
> Voice: 61-3-9337-6612
> Fantic 305, Hagar the Honda XR600RN
> ============================================================
Desert racers fit steering normal linear dampers under the headlight ( & above
the mudguard )across the bike . Other way for dirt bikes is the trick small
( & expensive ) rotary damper that fits on top of triple clamp stem.
Cheaper way is to just hang onto the bars tighter. IAN
Graham Byrnes
In article <01bc046a$c981c220$LocalHost@scott-young>, "Silk - Young"
<S...@onaustralia.com.au> wrote:
> Snip Snip Snip......
> > GOOOONNNNNNNNGGGGGGGGGGG!!!!!!!
> >
> > Hang on, hang on, it's the old 'centrifugal force' chestnut - wasn't it
> Prof
> > Julius Sumner-Miller who first said of centrifugal force that "There aint
> no
> > such animal"? Come on, Dr Graham, say something, I dropped physics after
>
> > first year.....
> >
> >
> > Sam (Boadicea's Mummy)
Sorry for neglecting my furphy-kicking duties, but I haven't seen the
original: my news link is Dawkinsed.
In brief, because to go round in cirles you must accelerate (change direction
=change velocity), force
is required acting towards the inside of the circle. This is called
centripetal force. It is provided by tyre-road friction. When the grip
isn't high enough you run wide or, if you have already leant far enough
to counter the grip that you expected, you fall down.
Think of being in a lift that is accelerating up. You feel the lift
floor push up against your feet so that your body will accelerate
upwards with the lift. OTOH, if you didn't know the lift was moving
you could explain this feeling by saying there was a strange force
pulling you down towards the bottom of the lift. That would be a fictitious
force, just like centrifugal force.
If however you are whizzing around a curve and don't want to know this,
you have to explain your body's desire to not go round the curve somehow,
so you invent a mythical force which is pulling your innards toward the
outside of the curve. This is called centrifugal force. Its legitimate
usage (Sam can claim this is work related) is for calculating corrections
when you lob artillery shells long distances on a rotating planet.
There is also another fictitious force which allows for the fact the earth
is spherical rather than cylindrical, called coriolus force, but that is rarely
invoked as a motorcycle stabilizer.
The thing wot keeps motorcyles stable is a combination of the angular
momentum of the wheels (which does depend on their radius, nyah nyah),
the steering geometry (rake, trail and tyre shape), the mass distribution
of the bike as a whole (high or low, front to rear, spread out or centralized)
and the rigidity of the whole thing (frame, tyre carcase strength, steering
head bearings and fork leg strength).
Cheers,
Graham
Baker@nabaus.com.au Matty
I have an XJ900 85 and on occasion I have the problem of getting the
speed wobbles through a corner. (Usually trying to take it faster than my
ability).
I was looking at fitting a damper but I am unsure of how to fit one.
Does anyone know the correct angle ranges the damper should be fitted and
where it should be located.
Ted Palmer
Matty <Matthew Ba...@nabaus.com.au> wrote:
[...]
>I was looking at fitting a damper but I am unsure of how to fit one.
On an XJ9? Shouldn't need one. However, the shaft drive would
complicate the equation a bit, too.
So, your handlebars have a nasty shake in fast corners?
I'd be more inclined to have a good look at the rear shocker
and the steering bearings, among other more conventional
woes including the fork oil.
Eg, at a Phillip Island ride day last year, the RC17 had a weave
that was bordering on disturbing. Those who know me may
wonder if I could become even more disturbed, but that's beside
the point. On fast right handers like up to Lukey, it gave cause
for concern.
Later, at the Netscrape, about the only difference was that the
rear shock was running with more air pressure, about 40-50psi
compared to the earlier 30-35psi. At the Netscrape, no more
weave. The other difference was the removed mirrors.
Which factor made the most difference? Dunno. I suppose I
could have made some scientific tests, but I was too busy
having fun and Prof Julius Sumner Miller never covered this
on TV.
Mister_T
"Like a bolt of lightning from the sky comes Honda's CBX750, the
fastest, brawniest 750 we've ever tested." Two Wheels, April 1984
peter....@dsto.defence.gov.au
>I was looking at fitting a damper but I am unsure of how to fit one.
>Does anyone know the correct angle ranges the damper should be fitted and
>where it should be located.
>
Try fitting anywhere that suits you. There are a few requirements:-
In traversing from lock to lock, the damper should cover almost all
of its travel -- this allows the greatest range of adjustment of the
perceived steering damping effect.
The mounts should be RIGID. The wobble you're concerned about probably
involves only a few degrees of steering movement, if your mounts flex
then the wobble ain't goin' to go away.
Try to achieve a setup which doesn't have part of the damper protruding
from the bike at extremes of lock - it results in snagged clothes and
a high risk of damper mortality.
The damper will generally work best with its axis at a right-angle to
the fork tubes.
The purpose of the unit is simply to place an upper limit on the rate at which
the steering may be turned -- there's no gotchas in it that I know of after
having used them for years.
Damian Carvolth
lots of big words snipped...
>The thing wot keeps motorcyles stable is a combination of the angular
>momentum of the wheels (which does depend on their radius, nyah nyah),
So your saying that an almost infinitely lightweight rim of large
diameter offers better centrifugal force than a smaller rim that's heavier ?
Note I said rim. And I'm not going to honour the validity of centrifugal
force argument with an answer, your being more pedantic than I was :)
I put it to you that it's the mass distribution depending on both weight
of rim and distance from center of rotation.
For those who aren't keeping up get a gyroscope and spin it. Then try and
rotate the center perpendicular to the plane of rotation. It resists,
and that's what keeps your bike up...
>the steering geometry (rake, trail and tyre shape), the mass distribution
>of the bike as a whole (high or low, front to rear, spread out or centralized)
>and the rigidity of the whole thing (frame, tyre carcase strength, steering
>head bearings and fork leg strength).
Yes.
Does that answer your question Sam ? :)
Graham Byrnes
In article <5c3u4j$v...@foxhound.dsto.gov.au>,
peter....@dsto.defence.gov.au wrote:
> The purpose of the unit is simply to place an upper limit on the rate at which
> the steering may be turned -- there's no gotchas in it that I know of after
> having used them for years.
>
bit tricky :-)
Graham
Zebee Johnstone
On 24 Jan 1997 07:02:19 GMT, Matt Baker <Matthe...@nabaus.com.au> wrote:
>Sounds like a course at a track is the way to go.
>
>Can anyone recommend a rider training course in the Melbourne area?
>
The Stay Upright advanced course was excellent, and they hold them in
Vic now and then. check http://www.ozemail.com/~stayup/home.html
(I think) for dates.
Zebee
Graham Byrnes
In article <5c129k$p...@mo.nabaus.com.au>, Matty <Matthew
Ba...@nabaus.com.au> wrote:
> I have an XJ900 85 and on occasion I have the problem of getting the
> speed wobbles through a corner. (Usually trying to take it faster than my
> ability).
I suspect that this might have more to do with nerves and clutching the bars
too tight because you are going faster than you feel comfortable with.
You could do a track-based riding course for less than the cost of a damper
(and it's easier to fit).
Graham
Baker@nabaus.com.au Matt Baker
Sam Michaelson
Damian Carvolth wrote:
>
> lots of big words snipped...
>
> >The thing wot keeps motorcyles stable is a combination of the angular
> >momentum of the wheels (which does depend on their radius, nyah nyah),
>
> So your saying that an almost infinitely lightweight rim of large
> diameter offers better centrifugal force than a smaller rim that's heavier ?
>
> Note I said rim. And I'm not going to honour the validity of centrifugal
> force argument with an answer, your being more pedantic than I was :)
>
> I put it to you that it's the mass distribution depending on both weight
> of rim and distance from center of rotation.
>
> For those who aren't keeping up get a gyroscope and spin it. Then try and
> rotate the center perpendicular to the plane of rotation. It resists,
> and that's what keeps your bike up...
I can remember a particularly graphic demonstration of this in a physics
lecture during a discussion of angular momentum. It involved a bicycle
wheel on a spindle, a swivel chair, and a very pretty young girl picked out
of the middle of the lecture theatre by the dirty old lecturer. (Sounds a
bit kinky so far, dunnit?) Anyway, the idea was that the assisting student
sat on the swivel chair, spun the bike wheel and held it out in front of
her, then the lecturer swiveled her around on the chair. The idea was to
demonstrate the difficulty then of tilting the bike wheel spindle through
ninety degrees, or something like that - I've long since forgotten the
derivation and the eventual equation, but I do remember the projectile
vomit spraying all around in a circle when she threw up. Strangely enough,
the lecturer was not so keen to let us discuss the phenomenon (doo doooooo
do doo doo) of recycled lunch travelling away from a spinning student
("Doesn't that make an argument for this centrifugal force thing then?"
"Nah, that's just it's velocity vector, see how it just kept going in a
straight line once it left her mouth...")
> >the steering geometry (rake, trail and tyre shape), the mass distribution
> >of the bike as a whole (high or low, front to rear, spread out or centralized)
> >and the rigidity of the whole thing (frame, tyre carcase strength, steering
> >head bearings and fork leg strength).
>
> Yes.
> Does that answer your question Sam ? :)
Duh..... now I remember why I ditched physics.
Sam (Boadicea's Mummy)
Abaddon
HONDA CX650E Vtwin water cooled, shaft drive. ( "The mighty Maggot.")
1983 model, 28000Km, excellent condition. Out of rego (who can afford
the green slips since deregulation made them cheaper ?) GIVI bags. $3300
o.n.o.
Phone (049) 67-5877 or 015 252 922
Graham Byrnes
In article <5c6pkl$m...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
Carvolth) wrote:
> lots of big words snipped...
>
> >The thing wot keeps motorcyles stable is a combination of the angular
> >momentum of the wheels (which does depend on their radius, nyah nyah),
>
> So your saying that an almost infinitely lightweight rim of large
> diameter offers better centrifugal force than a smaller rim that's heavier ?
Centrifugal, centripetal, whatever, it only determines how strong the spokes
have to be. Angular momentum determines how hard it is to deflect a
spinning wheel.
Also I said it depends on the radius, not that it depends *only* on the radius.
>
> I put it to you that it's the mass distribution depending on both weight
> of rim and distance from center of rotation.
Which I would agree is correct.
>
> For those who aren't keeping up get a gyroscope and spin it. Then try and
> rotate the center perpendicular to the plane of rotation. It resists,
> and that's what keeps your bike up...
That's *one* of the things that keep your bike up. It becomes more important
at high speed, but the rake and trail are always important: they tend to
automatically turn the front wheel into a lean, which then makes the bike come
up straight again.
Oh, I rode the new TZ on Saturday. 22 degree rake, 87mm trail and it's more
stable than my GSXR was. At least it's easier to control when it shakes
as the wheel comes up... power wheelstands? Who needs more than 250cc :-)
It does get a little nervous when the back wheel lifts off under brakes...
Graham
Tony Payne
Graham Byrnes (G.By...@latrobe.edu.au) wrote:
: In article <5c6pkl$m...@news.cat.csiro.au>, D.Car...@dem.csiro.au (Damian
: Carvolth) wrote:
: > lots of big words snipped...
...[Stuff about centripifugal force snipped 'n' shit snipped. We all know
bikes stay up coz they go fast]...
: Oh, I rode the new TZ on Saturday. 22 degree rake, 87mm trail and it's more
: stable than my GSXR was. At least it's easier to control when it shakes
: as the wheel comes up... power wheelstands? Who needs more than 250cc :-)
Details man, details!. Is the TZ new?. Did you test it in a race?. What mods
have you got planned?. When can I test ride it. ;-)
: It does get a little nervous when the back wheel lifts off under brakes...
Yeah. You need something like a CBR6 for that. 8-)
--
\|/ ____ \|/
@~/ ,. \~@
/_( \__/ )_\
+------------------------------\__U_/----------------------------------+
Tony Payne Phone: If Jim Morrison drove his van
Ynot Consulting 61 3 9557 8344 to Van Morrison's gym, would
Bentleigh Australia Would Don Johnson use the John
Email to...@replicant.apana.org.au in Van Johnson's van?.
Graham Byrnes
In article <85497080...@leon.replicant.apana.org.au>,
to...@replicant.apana.org.au (Tony Payne) wrote:
>
> Details man, details!. Is the TZ new?. Did you test it in a race?. What mods
> have you got planned?. When can I test ride it. ;-)
Sorry, my news reader has been spastic lately. No, they cost ~$38k new.
This is a '93 model... only planned mods are to the rider, since the bike
has circulated PI in 1'40" or so. Except for the paint.
First race is this w/e at Broadford, first round of the Vic titles/Challenge
cup. 37C in full leathers. Yeah.
Graham