Trouble with transmission?
silverdragon
When ever I am going slow the clutch has troble grabbing or somthing
and the scooter bumps and jerks arround and looses power like it's
catching an then not.
I don't know if this is a problem with the clutch, the drive belt or
the transmission.
I recently had the drive belt replaced and the rollers, and my vino is
all stock
I first had it happen when my wife and I were slowly navigating the
parking lot and I went over a speed hump and when I acellerated off it
started clunking and acting really weird when I was going slow. Right
away I had the belt and rollers replaced, because the mechanic said
that's what was causing it. Afterwards it was better for a few weeks
and then it started doing it agian, getting worse and worse. I have
found that if I acellerate really slow and give it power at just the
right time I can minimize or avoid the problem.
The vino btw has an automatic transmission.
Any help would be greatly apprecated!
- Eric
paul c
I doubt if it's caused by the transmission gears unless the gear oil has
never been changed, more likely the clutch is sticking, perhaps because
of wear or dirt or the clutch spring/springs are weak, especially if the
jerking is more pronounced with a passenger. That's assuming the
variator is clean, not warped and both the clutch and variator aren't
wobbling and also that the carb' is clean and adjusted right and the
brakes aren't grabbing. I think that worn rollers usually don't give the
symptom you mention. On the cvt's I've had, sticky clutches were
usually accompanied by a little brief grinding kind of noise which went
away after a few hundred miles. You need a service manual and a few
tools to check the clutch yourself.
paul c
It might help to isolate the problem by putting the scoot on the
centre-stand and turning the wheel with the engine off as well as
holding it with engine running and low throttle. Check for wobble too.
You might be able to notice a noise or erratic resistance on the clutch
end as opposed to the variator end or maybe even hear the rear brake
grabbing.
tomcas
It sounds like the belt may be too long or the variator is not down
shifting. In either case the person who replaced the belt and rollers
would seem to be responsible.
paul c
> silverdragon wrote:
>> ...
>> I first had it happen when my wife and I were slowly navigating the
>> parking lot and I went over a speed hump and when I acellerated off it
>> started clunking and acting really weird when I was going slow. Right
>> away I had the belt and rollers replaced, because the mechanic said
>> that's what was causing it. Afterwards it was better for a few weeks
>> and then it started doing it agian, getting worse and worse. I have
>> found that if I acellerate really slow and give it power at just the
>> right time I can minimize or avoid the problem.
>>
>> The vino btw has an automatic transmission.
>>
>> Any help would be greatly apprecated!
>>
>> - Eric
>
> It sounds like the belt may be too long or the variator is not down
> shifting. In either case the person who replaced the belt and rollers
> would seem to be responsible.
The OP wrote that he had the belt changed after it first happened.
tomcas
Isn't it possible that the original and replacement belts were both too
long and the symtoms appear after the belt wears? I got to add one more
possiblity - the variator spring may be weak or broken.
paul c
...
>> The OP wrote that he had the belt changed after it first happened.
>
> Isn't it possible that the original and replacement belts were both too
> long and the symtoms appear after the belt wears? I got to add one more
> possiblity - the variator spring may be weak or broken.
I believe those belts don't stretch much as they wear, rather they get
narrower between the edges and I doubt if the variator has a spring, in
three or four different cvt's I've had apart, none had a spring in the
variator, can't imagine what purpose one would serve.
So I'd still suspect the clutch (which does have springs). If I'm wrong
and the belt really is too long, the OP could easily check that with the
stock tool kit, just take of the transmission cover and look at the part
number on the outside of the bolt, make sure it's the right one. He'd
also be able to see if the variator faces are smooth and clean. But it
would be easier to guess if he had given more information, mileage,
other history, other maintenance etc, eg., if he's always riding two-up.
tomcas
You are correct, belts don't stretch at all, not even a little. But they
do wear by getting skinnier especially if they were too long to begin
with and as a result are constantly slipping and wearing out even
quicker. As the belt narrows it rides lower in the sheaves having the
same effect as a belt that's too long.
All variators have a huge compression spring that squeezes the rear
sheaves together. With out this spring the bike can't down shift. It's
impossible to service the clutch without first removing this spring. All
CVT scooters have them.
paul c
> ...
> You are correct, belts don't stretch at all, not even a little. But they
> do wear by getting skinnier especially if they were too long to begin
> with and as a result are constantly slipping and wearing out even
> quicker. As the belt narrows it rides lower in the sheaves having the
> same effect as a belt that's too long.
> All variators have a huge compression spring that squeezes the rear
> sheaves together. With out this spring the bike can't down shift. It's
> impossible to service the clutch without first removing this spring. All
> CVT scooters have them.
It could be that my terminology was too loose, it does seem that some
people refer to the whole assembly, the drive pulley and the driven
pulley as the variator. I was referring to the drive pulley, the one on
the crankshaft, which has no spring, at least on the typical scooter
cvt, maybe that's different for car cvts.
The picture for the Vino 125 at
http://www.bikebandit.com/houseofmotorcycles/yamaha-motorcycle-yj125v-vino125-2006/o/m8752
shows the big spring as number 23 on what Honda would call the driven
pulley, I'm not sure what Yamaha calls it. Lots of people call this
pulley the clutch and the drive pulley the variator, maybe that's
incorrect. It seems to me that it's not very helpful to refer to the
whole assembly, ie., both pulleys and the belt as the variator because
most of the time one is disassemblying one pulley or the other, not
both. Whatever the correct usage is, from now on, I'll try to avoid
confusion by referring only to the drive and driven pulleys.
SoCalMike
belt and rollers should be good for several thousand miles.. 8 or 12k.
if i was doing the work, id take it all apart, inspect the front and
rear pulleys, clean with denatured alcohol, check that it was
reassembled correctly, then take the bellhousing off (if thats the kind
of clutch it has), clean that, scuff sand the pads, and check all the
springs.
if it has a disc-type clutch, id check for contamination of the pads and
wear surfaces, and the springs.
SoCalMike
if they are using genuine yamaha parts, that shouldnt be an issue. id
vote for the springs, and a good cleaning.
SoCalMike
> tomcas wrote:
>
>> ...
>> You are correct, belts don't stretch at all, not even a little. But
>> they do wear by getting skinnier especially if they were too long to
>> begin with and as a result are constantly slipping and wearing out
>> even quicker. As the belt narrows it rides lower in the sheaves having
>> the same effect as a belt that's too long.
>> All variators have a huge compression spring that squeezes the rear
>> sheaves together. With out this spring the bike can't down shift. It's
>> impossible to service the clutch without first removing this spring.
>> All CVT scooters have them.
>
> It could be that my terminology was too loose, it does seem that some
> people refer to the whole assembly, the drive pulley and the driven
> pulley as the variator. I was referring to the drive pulley, the one on
> the crankshaft, which has no spring, at least on the typical scooter
> cvt, maybe that's different for car cvts.
you are/were correct. the variator is the front drive pulley with the
weights. the rear driven pulley is the clutch pulley. big spring in
there, and small springs holding the clutch in place. ive only had one
spring break before, on a helix, and it didnt do much aside from make a
"cling-cling" noise at idle/low speed.
if it has a "performance" belt or spring, id switch back to stock. i
tried one on a burgman and it only boosted the low range, at the expense
of gas mileage... about 10mpg drop. not worth it.
SoCalMike
> Okay, that is still more of a vibration than distinct jerks, but if
> your clutch bell is slightly out of round or has sticky spots, the
> combination of power strokes with shoes passing into less grippy parts
> of the bell, along with a third item -- slight warpage of the gear train
> adding a binding/release cycle.... I could see the behavior you see.
>
> Next time you try such slow speed maneuvers, try riding the rear
> brake (deliberately adding back pressure to the gear train and the rear
> pulley -- which should contribute to downshifting the pulleys) AND apply
> a slight bit more throttle. At some sweet spot you should have enough
> engine speed to smooth out the power on the slipping clutch, but also
> have the CVT in lowest gear so the speed is still under control.
one backyard "tune-up" method for the helix called for locking the rear
brake, then revving the engine for a couple seconds. that would
supposedly burn any contaminants off the pads and bellhousing. and
probably glaze the pads too!