CBX 750 gearbox sickness..
Col H
i was fanging around on me old CBX 750 a few months ago with me bro's
monster lurking on my tail, anyway .. after holding 10 grand in second in a
left hander, i now find that the bike changes up gears same as normal, but
its a demon to try and get it to downshift. usually takes 4 or 5 good taps
on the gearlever to get it to shift down.
it gets worse and worse the higher the gear used. i thought i may have bent
or cracked a selector fork. somebody else mentioned stuffed synchro rings.
does anyone have any idea what sort of problem i'm looking at ? i guess i'm
resigned to having to split the motor, but i'd like to know roughly what i'm
looking for before i start.
i hate gearbox problems, they always seem to cost megabucks.
Simon & Heidi Young
> usually takes 4 or 5 good taps on the gearlever to get it to shift down.
starting with the obvious, are you getting enough throw from the lever, ie
is the mechanism bottoming before a full shift is achieved? Something in the
lever system may be loose/bent/out of adjustment.
Something may be amiss in the ratcheting mechanism, broken return spring,
shattered pawl, debris floating about.
>
> it gets worse and worse the higher the gear used. i thought i may have
bent
> or cracked a selector fork. somebody else mentioned stuffed synchro rings.
a rooted dog ring will usually see it jumping out of gear on over-run,
should select fine. Forks may be bent or not running freely on support
rail, are you getting the dog/dog graunch as you miss a downshift?
>
> does anyone have any idea what sort of problem i'm looking at ? i guess
i'm
> resigned to having to split the motor, but i'd like to know roughly what
i'm
> looking for before i start.
>
> i hate gearbox problems,
I love gearbox jobs, well as long as they don't leave me stranded.
Simon
Col H
umm, shift seems fine when it does work, no graunching noises, or very rare
anyway. basically, when its not changing down, the lever is rock solid ..
doesn't move hardly at all. you can tap on the lever and it feels like its
welded to the sidecover. then it goes snick and changes fine.
its been a few months since i've ridden it, and have only rarely tried any
gears above about fourth since it happened. When it first happened it took
me 10 minutes i reckon, while moving, to get it from sixth to fifth. i was
still 100k's from home, by the time i got home it improved substantially,
which is why i thought of fork problems. maybe the fork had bent back into
shape ?
i've never had a good opportunity to study a bike gearbox, seen a few
exploded views tho'
so .. the shift lever operates a ratchet that rotates a drum about 20
degrees or so, that has the ends of the forks running in slots ... that
sound correct.
hmm, which means the drum is probably rotating freely, and the selectors
working ok .. but the ratchet is somehow jamming ?
<thinking of crossing fingers>
"Simon & Heidi Young" <mot...@netspace.net.au> wrote in message
news:8udsc0$1ouj$1...@otis.netspace.net.au...
SPAM"@winshop.com.au Andy
PVH cars, so I could be wrong. But as far as I am aware synchro rings are
there to make the gears mesh if the revs don't match the rear wheel speed.
Therefor if your doing clutch less down changes the synchro shouldn't make
any difference.
Assuming a bike gear box works in roughly the same way as a cars, the only
reason I can reason think of that the synchro could be causing problems with
clutch less changes is if the synchro gears are that buggered that they are
blocking the gears from meshing, if that situations is even possible, which
I would doubt because worn synchro gears would be more out of the way.
Any comments?
--
Andy
ZZR250
Col H <cols...@dingoblue.net.au> wrote in message
news:3a0a608d$0$19414$7f31...@news01.syd.optusnet.com.au...
> Hi all,
>
> i was fanging around on me old CBX 750 a few months ago with me bro's
> monster lurking on my tail, anyway .. after holding 10 grand in second in
a
> left hander, i now find that the bike changes up gears same as normal, but
> its a demon to try and get it to downshift. usually takes 4 or 5 good taps
> on the gearlever to get it to shift down.
>
> it gets worse and worse the higher the gear used. i thought i may have
bent
> or cracked a selector fork. somebody else mentioned stuffed synchro rings.
>
> does anyone have any idea what sort of problem i'm looking at ? i guess
i'm
> resigned to having to split the motor, but i'd like to know roughly what
i'm
> looking for before i start.
>
Doug Cox
<snip>
> Assuming a bike gear box works in roughly the same way as a cars,
They don't.
Doug Cox
Work to ride, Ride to work...
Doug...@Bigpond.com
http://www.users.Bigpond.com/Doug_Cox/
mick
mechanism in side the cases
but this is only a possibility
mick
"Col H" <cols...@dingoblue.net.au> wrote in message
news:3a0ad62e$0$19413$7f31...@news01.syd.optusnet.com.au...
Clem Doherty
the lever jammed?
Clem
Col H <cols...@dingoblue.net.au> wrote in message
news:3a0ad62e$0$19413$7f31...@news01.syd.optusnet.com.au...
Johno
> "Andy" <apcsystems"NO SPAM"@winshop.com.au> wrote in message
> <snip>
> > Assuming a bike gear box works in roughly the same way as a cars,
>
> They don't.
>
> Doug Cox
Constant mesh aint they Doug?
Johno
Doug Cox
news:01c04b04$0e5cf7a0$711f09d2@varcs...
> Doug informed us...
> > "Andy" <apcsystems"NO SPAM"@winshop.com.au> wrote in message
> > <snip>
> > > Assuming a bike gear box works in roughly the same way as a cars,
> >
> > They don't.
> >
> > Doug Cox
>
Yep.
Ted Palmer
>Hi all,
>
>i was fanging around on me old CBX 750 a few months ago with me bro's
>monster lurking on my tail, anyway .. after holding 10 grand in second in a
>left hander, i now find that the bike changes up gears same as normal, but
>its a demon to try and get it to downshift. usually takes 4 or 5 good taps
>on the gearlever to get it to shift down.
[...]
This sounds a lot like what happened to my bike.
It turned out to be one of the little springs in the selector ratchet
system.
It's not a hard fix at all since Honda had the great foresight to have
a separate cover on the LH case just for the ratchet system.
Maybe it's just an expected thing with a 6-speed 16-yo sports bike.
The parts are not expensive, you might get away with one spring and a
gasket, but you might as well get both ratchet springs as the upshift
one won't be far behind the (what I suspect) the failed one.
Are you in Melbourne? If you are then I can help you with the
inspection and maybe I could take some pics of the procedure for the
Team RC17 website (some might say "the best CBX750 website in the
world").
An RC17 box is a reasonably tough device despite the builtin backlash.
When they get really old they tend to jump out of the lower gears.
I have nearly 100,000km on mine and don't have the gear jumping yet.
Mister_T
Team RC17 Australia: Knocking on Death's door, then running away.
--
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\
| See the dubious rantings of Team RC17 at |
| http://replicant.apana.org.au/~viking/ |
\|_________________________________________________________________|
Col H
no, I'll be right, i was sent an email by 'viking' that pointed me to the
website. i had searched for CBX info a few months ago and came up mostly
blank, i'll know better next time and search for RC17 ..
the only thing that is starting to annoy me now on this whole broken spring
now, is that of the 6 or so bike mechanics i've mentioned it too, they all
hummed and haa'ed about it being 'nasty' and a big job .. they all looked a
bit shifty as they discussed it though, so i kept asking more. I suppose its
not in their interest to tell me its only a little spring and a minor job
though.
I have a digital camera handy at times, so i'll be sure to post some photos
of the job when i get round to doing it (maybe this afternoon).
anyway, now i've found the CBX750 nutters, you won't get rid of me that
easily. I've had it 8 years, still no reason to sell it yet.
"Ted Palmer" <te...@SPAMOFF.replicant.apana.org.au> wrote in message
news:3a0c0421...@replicant.apana.org.au...
Simon & Heidi Young
> > >
> > > They don't.
> > >
> > > Doug Cox
> >
>
> Yep.
>
They're all constant mesh, its the method of engaging the gear with the
mainshaft that varies (synchro vs dog)
Simon
Ted Palmer
>hehe. thanks Mr_T (nice CBX you have btw)
I look after it, it looks after me.
>no, I'll be right, i was sent an email by 'viking' that pointed me to the
>website. i had searched for CBX info a few months ago and came up mostly
>blank, i'll know better next time and search for RC17 ..
What do you search with? Many of the hits on AltaVista under "CBX750"
tend to be from sections of the Team site.
>the only thing that is starting to annoy me now on this whole broken spring
>now, is that of the 6 or so bike mechanics i've mentioned it too, they all
>hummed and haa'ed about it being 'nasty' and a big job .. they all looked a
>bit shifty as they discussed it though, so i kept asking more. I suppose its
>not in their interest to tell me its only a little spring and a minor job
>though.
Most of them probably don't even remember what a CBX750 looks like,
and most likely don't know that there is a separate cover for the
shifter ratchet.
The hard thing is picking the difference between the genuinely
ignorant and the shonks.
>I have a digital camera handy at times, so i'll be sure to post some photos
>of the job when i get round to doing it (maybe this afternoon).
Geez, I hope you remember to drain the sump first.
As well, you'd need a real macro lens to take a proper pic of one of
those tiny ratchet pawl springs.
>anyway, now i've found the CBX750 nutters, you won't get rid of me that
>easily. I've had it 8 years, still no reason to sell it yet.
See you on our mailing list, then. We need some more aussie owners on
the list, we're outnumbered by the Poms.
Mister_T
"All-out sport riders will be immensely pleased with the bike's
acceleration, speed, stability and general handling"
AMCN CBX750F road test, March 1984
--
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\
| RC17 KLR600 Roces BCN FreeBSD 2.2.5-R NT4W (Not Tenable)|
| tedp[at]replicant[dot]apana[dot]org[dot]au |
\|_________________________________________________________________|
Col H
> tend to be from sections of the Team site.
hmm, i used altavista about 6 weeks ago, with that very search and came up
with nada ..
>
> Most of them probably don't even remember what a CBX750 looks like,
> and most likely don't know that there is a separate cover for the
> shifter ratchet.
> The hard thing is picking the difference between the genuinely
> ignorant and the shonks.
>
very true, dunno which is worse anyway. i have only just moved here, so its
a good excercise to discover who i should go to if in need of a professional
mechanic.
>
> Geez, I hope you remember to drain the sump first.
> As well, you'd need a real macro lens to take a proper pic of one of
> those tiny ratchet pawl springs.
i ain't that thick :)
pics are up at
http://members.dingoblue.net.au/~colstoney/serve/rc17__ratchet_spring_repla.
htm
if you are interested.
>
> See you on our mailing list, then. We need some more aussie owners on
> the list, we're outnumbered by the Poms.
>
finally .. the poms show some class ;)
> Mister_T
>
> "All-out sport riders will be immensely pleased with the bike's
> acceleration, speed, stability and general handling"
> AMCN CBX750F road test, March 1984
i like that sig line .. but i'd remove the date :)
Ted Palmer
[...]
>hmm, i used altavista about 6 weeks ago, with that very search and came up
>with nada ..
Sometimes you have to wade through people's pics of their Horizon
(ergh, horrible abberation using the RC17 motor) or Nighthawk (seems
very similar to the CB Seven Fifty that came to Oz) which are
somewhere next to the pic of the pet rocks or something.
I just did a search and a link to the RC17 picture section came up in
the first ten hits. Whatever.
[...]
>very true, dunno which is worse anyway. i have only just moved here, so its
>a good excercise to discover who i should go to if in need of a professional
>mechanic.
Most routine things on the RC17 don't need a fancy mechanic, luckily.
I got lazy and let someone else do my camchain a while ago.
I have a carby balancer now so that is no longer a shop job.
>> Geez, I hope you remember to drain the sump first.
>> As well, you'd need a real macro lens to take a proper pic of one of
>> those tiny ratchet pawl springs.
>
>i ain't that thick :)
Heh, a bloke I know who owned a CBX before I did didn't even know that
you have to drain the frame rails during an oil change.
>pics are up at
>http://members.dingoblue.net.au/~colstoney/serve/rc17__ratchet_spring_repla.
>htm
>if you are interested.
Nice camera work. Can we rip off the page for the Team site?
I can see this little quirk of the bike might apply to all owners at
some stage.
[...]
>> "All-out sport riders will be immensely pleased with the bike's
>> acceleration, speed, stability and general handling"
>> AMCN CBX750F road test, March 1984
>
>i like that sig line .. but i'd remove the date :)
I believe in truth-in-advertising.
There are plenty more sigs where that one came from.
If I left out the whole line containing the bike name, the quote could
apply to just about any sportsbike made in the last 20 years. You
wouldn't know if it was a RC07/15 (VF750F RC07-frame, RC15-engine, umm
or is it the other way around) or a Fireblade (PCsomething).
Some things like magazine tests don't change.
Mister_T
"The gearchange was mostly so slick in operation that I hardly noticed
it." UK "Mechanics" magazine CBX750F test, June 84
--
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\
| RC17 KLR600 Roces BCN FreeBSD 2.2.5-R NT4W (yik) |
Col H
up
> >with nada ..
>
> (ergh, horrible abberation using the RC17 motor) or Nighthawk (seems
> very similar to the CB Seven Fifty that came to Oz) which are
> somewhere next to the pic of the pet rocks or something.
> I just did a search and a link to the RC17 picture section came up in
> the first ten hits. Whatever.
yeh, ran it again this morning, and it was number 9 i think. i swear i
checked every link in the first 30 last time, <shrug> maybe i had brain
fade.
> Most routine things on the RC17 don't need a fancy mechanic, luckily.
> I got lazy and let someone else do my camchain a while ago.
> I have a carby balancer now so that is no longer a shop job.
>
I've never used a professional mechanic on any vehicle i've ever owned, mind
you, some of them died horrible slow deaths.
I was going to build a 4 way EGT monitor to help me with my carby problems,
they are next on the list. Actually i should order some new manifolds, mine
are rooted.
>
> Heh, a bloke I know who owned a CBX before I did didn't even know that
> you have to drain the frame rails during an oil change.
>
actually, was going to mention this, my bike always takes nearly litre more
than the specs, almost 5 litres for a full change. Have you found the specs
wrong on oil capacity ?
> >pics are up at
>
>http://members.dingoblue.net.au/~colstoney/serve/rc17__ratchet_spring_repla
.
> >htm
> >if you are interested.
>
> Nice camera work. Can we rip off the page for the Team site?
> I can see this little quirk of the bike might apply to all owners at
> some stage.
I wouldn't rip the page, its pretty crappy, but you are welcome to any of
the pics on it .. i haven't finished yet since its not all back together and
running, i may find something else that needs noting.
I just ordered the springs from Honda $6.60 for 2. if i remember i'll write
the part number in too. took em quite a while to hunt it down on the 'fiche.
(basically till they turn the damn thing round so you can help)
> Mister_T
>
> "The gearchange was mostly so slick in operation that I hardly noticed
> it." UK "Mechanics" magazine CBX750F test, June 84
hah, how apt .. my down changes are so slick that the bike doesn't notice it
either. (or change gear for that matter)
Hmm, if this problem ever occurred on the road in between burke and ...
ummm. .. somewhere else that has a road to burke, i suggest an emergency
repair would be to remove the broken spring and place the spring from
underneath the ratchet into the top hole. gravity would probably replace the
lower spring in an emergency. in fact how wonder how many may have the lower
spring broken and the owners don't know, possibly you would just get the
occasional missed upshift.
the lower spring on mine shows quite a bit of wear too, it didn't have long
for this world.
again .. thanks for the help.
Col (with a big cheesy grin)
Ted Palmer
>they are next on the list. Actually i should order some new manifolds, mine
>are rooted.
Yow, keep that camera handy.
[oil change]
>actually, was going to mention this, my bike always takes nearly litre more
>than the specs, almost 5 litres for a full change. Have you found the specs
>wrong on oil capacity ?
Never measured it, I just tip oil in to fill, run it a bit then top
up.
[shift ratchet pics]
>I wouldn't rip the page, its pretty crappy, but you are welcome to any of
>the pics on it .. i haven't finished yet since its not all back together and
>running, i may find something else that needs noting.
Beautay.
>I just ordered the springs from Honda $6.60 for 2. if i remember i'll write
>the part number in too. took em quite a while to hunt it down on the 'fiche.
>(basically till they turn the damn thing round so you can help)
I might be able to locate the part numbers as I most likely kept the
receipts for my parts. I replaced a few other parts in there as well
but in hindsight they weren't needed.
You could beat the counter jockeys at their own game if you get your
own set of fiche and a secondhand fiche reader.
It was only about $11 for the parts fiche I bought a while back and
maybe $20 for the reader.
I'm told the shop manual is available on fiche as well.
[...]
>Hmm, if this problem ever occurred on the road in between burke and ...
>ummm. .. somewhere else that has a road to burke, i suggest an emergency
>repair would be to remove the broken spring and place the spring from
>underneath the ratchet into the top hole. gravity would probably replace the
>lower spring in an emergency.
Agreed.
> in fact how wonder how many may have the lower
>spring broken and the owners don't know, possibly you would just get the
>occasional missed upshift.
Quite a few I suspect. AFAIR, my lower spring had broken but the coils
had bound together and it still worked enough.
I suspect that most of my occasional missed upshifts were caused by
being lazy, compounded by not having a muffler on the LHS to brace the
rubber mounted footpeg hanger.
>the lower spring on mine shows quite a bit of wear too, it didn't have long
>for this world.
In theory, the best way to take the load off the springs while parked
is to leave the bike in gear. From what I remember, both ratchet pawl
springs are compressed when the box is in neutral.
Mister_T
"Honda's CBX750F is a stunning piece of engineering"
AMCN CBX750F road test, March 1984
--
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\
| RC17 KLR600 Roces BCN FreeBSD 2.2.5-R NT4W (ugh) |
Neil Milne
Yer Col, ya just need a 2nd hand fiche reader ;D
Col H
i wondered where that ended up :)
its ok, i can't find the 'fiche at the moment anyway.
now to try and fix the oil leaks :(
"Neil Milne" <nmi...@bigpond.com> wrote in message
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