"Engine braking" on a two stroke
Torben Hedstrøm
What actually happens, if you do this on a two stroker ?, does it wear
the piston-rings because of lack of lubrication ?, or can you do it
reguarly without worrying ?. What I'm talking about is ofcourse
releasing the throttle, to have the braking effekt, or just to correct
speed !!!.
I've discussed it with a few friends, but none of them has any
experience with this. Hope you can help me.
Janet Penelope Gunn
In <msg116426.thr...@online.pol.dk>
Torben_...@online.pol.dk (Torben =?iso-8859-1?q?Hedstr=F8m?=)
writes:
>What actually happens, if you do this on a two stroker ?, does it wear
>the piston-rings because of lack of lubrication ?, or can you do it
>reguarly without worrying ?. What I'm talking about is ofcourse
>releasing the throttle, to have the braking effekt, or just to correct
>speed !!!.
>
Using what little engine braking you have shouldn't hurt in most cases
(e.g changing down for a corner). I wouldn't, however, run down a
long, steep hill with the throttle closed. At least not if I were
running premix. An oil pump might (or might not) pump enough oil to
keep everything healthy.
Janet Gunn
Graham Byrnes
In article <5rgeu4$m...@sjx-ixn4.ix.netcom.com>, jg...@ix.netcom.com(Janet
Penelope Gunn ) wrote:
> In <msg116426.thr...@online.pol.dk>
> Torben_...@online.pol.dk (Torben =?iso-8859-1?q?Hedstr=F8m?=)
> writes:
> >
> >What actually happens, if you do this on a two stroker ?, does it wear
> >the piston-rings because of lack of lubrication ?, or can you do it
> >reguarly without worrying ?. What I'm talking about is ofcourse
> >releasing the throttle, to have the braking effekt, or just to correct
> >speed !!!.
> >
> First of all, you don't GET much engine brakeing from a 2stroke.
>
> Using what little engine braking you have shouldn't hurt in most cases
> (e.g changing down for a corner).
I'm quite happy to bang down gears near the apex of a corner, unless it's
2nd to 1st which can break traction. OTOH some bikes will seize running
into fast corners on a closed throttle after a long straight: TZ125's are
known for it unless you do some fiddling with the carby.
Don't forget Doohan lost a race to Criville last year when he shifted to 1st
instead of 2nd and hung a biiig slide.... but that was a 500 and MD rides
with less margin for error than you or I.
Graham
Janet Penelope Gunn
In article <G.Byrnes-280...@graham-byrnes.maths.latrobe.edu.au>,
G.By...@latrobe.edu.au (Graham Byrnes) wrote:
>I'm quite happy to bang down gears near the apex of a corner, unless it's
>2nd to 1st which can break traction. OTOH some bikes will seize running
>into fast corners on a closed throttle after a long straight: TZ125's are
>known for it unless you do some fiddling with the carby.
>
As I understand it, that kind of seizure has to do with reducing the flow
of cooling mixture when you close the throttle. It wouldn't matter whether
the clutch was in or out, and is not related to engine braking, per se.
Janet Gunn
Benjamin Justin Cain
Graham Byrnes (G.By...@latrobe.edu.au) wrote:
:
: 2nd to 1st which can break traction. OTOH some bikes will seize running
: into fast corners on a closed throttle after a long straight: TZ125's are
: known for it unless you do some fiddling with the carby.
So are RDs, if memory serves. Whaddya say, Richard?
;)
--
Ben Cain : Biker Scum - Yellowshirt Brigade #514
AMA HRCA TMGP CMRA/WERA DoD # 1/137 KoK3
1990 VFR750F "Deal's Gimp"
1989 YSR50/3
1988 Ninja 600
http://www.users.cts.com/king/d/drlubell/bscum.html
"If I start bawlin', will you hold me?"
-Biker Scum Dave-
Richard Hill
Benjamin Justin Cain wrote:
>
> Graham Byrnes (G.By...@latrobe.edu.au) wrote:
> :
> : 2nd to 1st which can break traction. OTOH some bikes will seize running
> : into fast corners on a closed throttle after a long straight: TZ125's are
> : known for it unless you do some fiddling with the carby.
>
> So are RDs, if memory serves. Whaddya say, Richard?
>
> ;)
>
Hey,
I resemble that remark.
Been there,
Done that,
Got the seizure (t-shirt ... seizure .... never mind)
--
Richard Hill
http://www.flash.net/~rwhill/
CMRA #414 Sprints - #14 YSR Endurance
TMGP #18
Houston, Texas
Graham Byrnes
In article <5rib25$k...@sjx-ixn3.ix.netcom.com>, Janet Penelope Gunn
<jg...@ix.netcom.com> wrote:
> >2nd to 1st which can break traction. OTOH some bikes will seize running
> >into fast corners on a closed throttle after a long straight: TZ125's are
> >known for it unless you do some fiddling with the carby.
> >
> As I understand it, that kind of seizure has to do with reducing the flow
> of cooling mixture when you close the throttle. It wouldn't matter whether
> the clutch was in or out, and is not related to engine braking, per se.
Could be... I would have guessed that spinning the motor fast with no cooling
mixture would be worse than spinning it slowly, but maybe not.
What I find strange is that part of the cure seems to be drilling the slides
at the top. This I would have expected to lean the mixture on a closed
throttle... although maybe it balances out with the bigger pilot jet?
Cheers,
Graham
Leland Kornhaus
Benjamin Justin Cain wrote:
> Graham Byrnes (G.By...@latrobe.edu.au) wrote:
> : 2nd to 1st which can break traction. OTOH some bikes will seize running
> : into fast corners on a closed throttle after a long straight: TZ125's are
> : known for it unless you do some fiddling with the carby.
> So are RDs, if memory serves. Whaddya say, Richard?
RDs used Yamaha's autolube system (Yamalube!?). A pump,
geared to the engine would stroke at a fixed rate with
respect to the engine: doubling engine speed would double
the rate. If you think about it, this alone is not enough:
at WOT much more gasoline is moving through the carbs than
at partial throttle. Thus, there was a second component
to the system. Attached to the throttle cable was an extra
cable which went to the pump. This cable turned a cam which
increased the length of the stroke as throttle increased.
The two stroke oil moved from the pump and into the carbs.
I believe it mixed with the gasoline in the float bowl, but
could be wrong - it may have gone directly to the intake to
the reeds. (Richard Hill can correct me on this.) At any rate,
high revs coupled with closed throttle really cuts back on
both the amount of oil and gas seen by the engine. This is
as bad as you'd expect - particularly if the cam which controlled
the oil pump stroke at closed throttle was adjusted wrong.
I believe Keith Code, in "The Soft Science of Roadracing
Motorcycles" cautions against dependance on engine braking
and suggests setting idle at 3000-4000 rpm until you've
learned to rely on your real brakes.
-Leland
Elvis Presley
In article <33DDDF0E...@tellabs.com>, Leland Kornhaus
<korn...@tellabs.com> writes
>I believe Keith Code, in "The Soft Science of Roadracing
>Motorcycles" cautions against dependance on engine braking
>and suggests setting idle at 3000-4000 rpm until you've
>learned to rely on your real brakes.
I have had to do this after switching from a 2 stroke to a 4 stroke to
try to stop me from locking up the rear on downshifts. I am now starting
to learn a *little* bit of finesse with the clutch ;-)
--
The King <el...@presley.demon.co.uk>
Moped Racer Online Magazine.
Moped Mayhem Results Service, and comprehensive moped racing news
and info pages.
<http://www.presley.demon.co.uk>Last update:24.06.97
Richard Hill
Leland Kornhaus wrote:
>
> Benjamin Justin Cain wrote:
>
> > Graham Byrnes (G.By...@latrobe.edu.au) wrote:
>
> > : 2nd to 1st which can break traction. OTOH some bikes will seize running
> > : into fast corners on a closed throttle after a long straight: TZ125's are
> > : known for it unless you do some fiddling with the carby.
>
> > So are RDs, if memory serves. Whaddya say, Richard?
So's any 2-stroke, if piston clearance is reduced to zero :)
>
> The two stroke oil moved from the pump and into the carbs.
> I believe it mixed with the gasoline in the float bowl, but
> could be wrong - it may have gone directly to the intake to
The oil inlet was past the slide and float bowl. No float bowl mixing
done. Oil was injected directly in the air stream just ahead of the
reed cage.
Seizures are a by-product of one predomnant situation.
Lack of piston clearance.
Oils _primary_ purpose in 2-strokes is to lube the crank, not prevent
seizures.
> I believe Keith Code, in "The Soft Science of Roadracing
> Motorcycles" cautions against dependance on engine braking
> and suggests setting idle at 3000-4000 rpm until you've
> learned to rely on your real brakes.
>
> -Leland
Janet Gunn
In article <33DDF4...@flash.net>,
Richard Hill <tws...@flash.net> wrote:
>Seizures are a by-product of one predomnant situation.
>
>Lack of piston clearance.
>
Seizures have one primary cause - overheating the piston.
This may be from running too lean, or from detonation (either
from the wrong ignitiion timing, the wrong octane, or the wrong
plug), or from blowby (related to worn rings and or excessive
piston clearance). With more piston clearance, the piston
has to get hotter before it sticks, so having inadequate piston
clearance may increase your chances of having a seizure,
but I wouldn't call it the primary cause.
Janet Gunn
Richard Hill
Pat Farrell wrote:
> Most of mine were ignition timing related, once I started using real
> gasoline. Only once did I squeek one, a new TZ250F at Rockingham,
> when it went too lean after I shut down for the checkered flag.
>
> Ob subject, of course, when the engine seizes, it is really effective
> as a brake.
I have a lump on my left clavicle as a result of 'sudden unexpected
engine breaking/braking' (and in this case, bone breaking) :)
>
> Pat
>
> Pat Farrell CyberCash, Inc. (703) 715-7834
> pfar...@cybercash.com
> #include standard.disclaimer
Pat Farrell
Leland Kornhaus <korn...@tellabs.com> wrote:
>RDs used Yamaha's autolube system (Yamalube!?). A pump,
>geared to the engine would stroke at a fixed rate with
>respect to the engine: doubling engine speed would double
>the rate. If you think about it, this alone is not enough:
>at WOT much more gasoline is moving through the carbs than
>at partial throttle. Thus, there was a second component
>to the system. Attached to the throttle cable was an extra
>cable which went to the pump. This cable turned a cam which
>increased the length of the stroke as throttle increased.
On a race track (this is a race-oriented group, right), especially
with an underpowered bike like a RD350, you run with lots of throttle
most of the time, so there is lots of oil. There is residual oil still
in the system to handle when the throttle is shut during braking.
Back in the 70s, when RDs were new, many (most?) racers adjusted the
cable and cam so that no oil was pumped at idle, and then threw in
a few ounces of oil in the tank. WERA rules at the time required
pumps, altho more than one racer removed the gearing
and pump internals to "save weight" and ran premix.
Janet's post is correct. Two strokes seize when the piston is too hot.
While too much or too way little clearance will cause a seizure,
this is not generally a problem. Too much clearance prevents heat
transfer to the cylinders. Too little is obvious, but mostly occurs
when the cylinders are no longer round and straight.
Most of mine were ignition timing related, once I started using real
gasoline. Only once did I squeek one, a new TZ250F at Rockingham,
when it went too lean after I shut down for the checkered flag.
Ob subject, of course, when the engine seizes, it is really effective
as a brake.
Pat
Dennis McGuire
On Tue, 29 Jul 1997, Leland Kornhaus wrote:
Yamalube is their oil, Autolube was the injection system. The oil
was mixed with the fuel in the throat of the carburetor. The Suzuki
system was much better in that it pumped oil directly to the main bearings
also.
> Benjamin Justin Cain wrote:
>
>
> RDs used Yamaha's autolube system (Yamalube!?). A pump,
> geared to the engine would stroke at a fixed rate with
> respect to the engine: doubling engine speed would double
> the rate. If you think about it, this alone is not enough:
> at WOT much more gasoline is moving through the carbs than
> at partial throttle. Thus, there was a second component
> to the system. Attached to the throttle cable was an extra
> cable which went to the pump. This cable turned a cam which
> increased the length of the stroke as throttle increased.
>
> The two stroke oil moved from the pump and into the carbs.
> I believe it mixed with the gasoline in the float bowl, but
> could be wrong - it may have gone directly to the intake to
> the reeds. (Richard Hill can correct me on this.) At any rate,
> high revs coupled with closed throttle really cuts back on
> both the amount of oil and gas seen by the engine. This is
> as bad as you'd expect - particularly if the cam which controlled
> the oil pump stroke at closed throttle was adjusted wrong.
>
Claudio Bonavolta
Torben Hedstrøm wrote:
> What actually happens, if you do this on a two stroker ?, does it wear
>
> the piston-rings because of lack of lubrication ?, or can you do it
> reguarly without worrying ?. What I'm talking about is ofcourse
> releasing the throttle, to have the braking effekt, or just to correct
>
> speed !!!.
>
> I've discussed it with a few friends, but none of them has any
> experience with this. Hope you can help me.
>
> Torben_...@online.pol.dk
Hi Torben,
There are no problems at all when you close the throttle, the slow jet
is still releasing petrol and oil, enough to normally avoid a seizure.
You would have a seizure when your settings (main jet, ignition advance,
needle, petrol quality or compression ratios) are already to the limit,
closing the throttle at that time could do it but not normally ...
If you need more info about carburation, give a look to my site.
--
Regards,
Claudio Bonavolta
bo...@swissonline.ch
http://www.infomaniak.ch/~bonavolt/index.htm
Ian Drysdale
> > I believe Keith Code, in "The Soft Science of Roadracing
> > Motorcycles" cautions against dependance on engine braking
> > and suggests setting idle at 3000-4000 rpm until you've
> > learned to rely on your real brakes.
> >
> > -Leland
I haven't read this thread for a while and the discussion
has turned to oiling.
My comment on engine braking - if you think a 2 stroke has
no engine braking have a ride on a Husky auto some time.
They have 'sprag clutches' ( one way bearings) in the
transmission and have NO engine braking at all - I mean none
- not a scrap.
It is a very disconcerting feeling at first - some people
just never get used to it. The autos are a love/hate
thing - and it is usually love or hate at first sight ( or
ride ) I've had 2 and regret selling them both.
Cheers IAN
Kevin Frost
There is none!!
Kevin Frost
98/GPZ-500RR
Matthew Chute
Kevin,
I have a 900rr and am getting into racing. Due to the rules of
Amateur/expert I can't race it so I was thinking about 250gp.
I know this is kind of a broad question but: Is 250gp a good inexpensive
class to race in or am I heading for mechanical and costly nightmare?
Matt
J
(although relatively easy) maintenence.Second,although a 250 is easy to
ride,it takes a fairly high skill level to ride fast.Your best bet for
learning is an EX500 or the like--preferably stock,find an ugly one for
a grand and ride the snot out of it!(see the FAQ for reference to the
new racers newsletter)And as far as cost,well there are guys running
250s on a shoestring,but your still looking at 1 crank rebuild ($600),4
top ends($500), 2 sets of tires($600),and general tuning,oil,and RACE
gas($500) at the bare minimum for a 6-8 weekend season.You don't want to
know what a fully dedicated club (let alone AMA) season could run
you!Good luck,no matter what you decide on!
Jay
93-96 TZ250 AMA#77
97 YZ250 CCS#7
88 DR100 WERA#352
90 TZ250 For Sale!
Tim
What about the 125's?. Would one be looking at comparable maintenance
expenses with them as compared to the 250's?. I'm thinkin' about doing
some of the southeastern WERA & CCS races next year, and I figured a 125
would be loads o' fun. I'll definitely be running a '72 CB350 in AHRMA
vintage next year (real cheap racing), but those 125's sure look like
they'd be fun to race. Comments?.
Thomas Di Nardo
Kevin -
I think a 125 would be a better starting point if you want to run a
2-stroke. Much cheaper on tires and maintenance. 250's are a lot of fun,
but I wouldn't recommend starting on one. A 125 will teach you how to go
fast - very high corner speed, great brakes, etc.
Good luck.
Thomas Di Nardo
Dinar Leathers
AMA PRO 250GP #38
Richard Hill
The cheapest and best 'starter' bike IMHO would be the YSR. Lots of
organizations catering to just the YSR. You learn how to 'ride in
traffic' ... but at a considerably slower speed so there is less fear of
'get-offs'. You learn how to keep corner speeds up, because you have no
motor to pull you out of a corner. Lots of cheap knee-draggin' fun.
Just ask Colin Edwards. He started on the YSR ... and recommends them.
You can pick up a race ready bike for less than $1000 (often for half
that much), and good race tires are less than $125 a _set_ ... not
each. Several companies offer go-faster goodies for them. I have
improved my lap times significantly on my big bike because of the seat
time on the YSR.
My vote is for the YSR.
Benjamin Justin Cain
Richard Hill (tws...@flash.net) wrote:
: The cheapest and best 'starter' bike IMHO would be the YSR. Lots of
: organizations catering to just the YSR. You learn how to 'ride in
: traffic' ... but at a considerably slower speed so there is less fear of
: 'get-offs'. You learn how to keep corner speeds up, because you have no
: motor to pull you out of a corner. Lots of cheap knee-draggin' fun.
: Just ask Colin Edwards. He started on the YSR ... and recommends them.
: You can pick up a race ready bike for less than $1000 (often for half
: that much), and good race tires are less than $125 a _set_ ... not
: each.
Not only that, but they last a whole season!
: My vote is for the YSR.
Also be aware that only racing a YSR will prepare you to shudder and
babble incoherently after your first stint on a big bike. I was AMAZED
at how short and skinny the Oak Hill track became when I took it on the
Ninja. And that was only practice. After the actual RACE at TWS, I
went into a coma for several days just from the adrenaline.
--
Ben Cain : Biker Scum - Yellowshirt Brigade #514
AMA HRCA TMGP CMRA/WERA DoD # 1/137 KoK3
1990 VFR750F "Deal's Gimp"
1989 YSR50/3 TMGP Endurance #49
1988 Ninja 600 CMRA Endurance #46
http://www.users.cts.com/king/d/drlubell/bscum.html
"So basically if we hit turn one wide open, we oughtta be ok. Right?"
- BS Nathan, waxing philosophical at Texas World Speedway -