34 replies to this topic

[thefleshrocket]

I've put a few hundred miles on a new-to-me '99 VFR. It would shudder when engaging the clutch from a dead stop and, when upshifting at or close to WOT, it wouldn't re-engage as quickly as it should have. It would also occasionally "slip then grip" while in second gear under WOT, usually in the 8-10K range.

I replaced the clutch friction plates and the springs with EBC parts and all of the issues are gone--except for the slip then grip. What basically happens is that the engine RPM will jump up a thousand RPM or so for a split second and then settle back down to where it should be. It will only do it once while accelerating up through the gears, and so far I think it has only done it in second gear.

WHen changing the friction plates, I noticed that several of the steel plates were discolored or even burned looking. I've ordered a set of steels and am pretty sure that'll solve the problem. I thought it might be an issue with the trans slipping out of gear, but if that was the case, it shouldn't re-engage--instead it should false-neutral. And if it was slipping out of gear and back in, I'd think that it would do so with a bang--when the RPM drop back to where it should be, it does so firmly but not jarringly.

So, while I'm waiting for the steels to arrive, do you guys think they'll fix the problem or should I plan on dropping the motor to replace the transmission dogs this winter? LOL

Edited by thefleshrocket, 12 October 2011 - 09:22 PM.

[PhotoOp]

Sounds clutch related to me, transmissions usually bang back in, not slip like that

[gll429]

did you SOAK the plates in oil before you installed them??? if not.. do so. it makes a HUGE difference.

[thefleshrocket]

Yup, I did soak the plates for about an hour before installing. Before changing the clutch, I changed the oil (with Amsoil 10W40) too, just in case the PO had used the "wrong" oil. Finger crossed that it's the steels--I don't think I want to spend a day or two changing out trans parts! The trans itself seems to shift smoothly with no false neutrals or slipping out of gear, so I'm reasonably confident it's in good shape.

[gmtech94]

Also check the clutch cylinder as it may have some crud built up on it not allowing the rod to fully disengage . It is a common problem with a bike this age .

[baldyjoe]

try changing and bleeding the clutch master and slave cylinder.

[thefleshrocket]

I've replaced the steels. After installing them, the slip/grip still remains.

The symptoms:
--The engine RPM climb about 1000 or so, then almost instantly drop down to
where they should be.
--It happens at different RPM but usually in the 6,000-11,000 range.
--It only seems to happen in 2nd gear. I've tried to duplicate in 3rd but
haven't been able to do so, and none of the other gears have exhibited the
symptom either despite heavy acceleration.
--It only happens once during an acceleration run. IE if it happens at
7000RPM, it won't happen a second time during the run.
--It happens more often when the engine oil is cooler--after riding for
about 15 minutes today (55F ambient), it did it under a 3/4 throttle burst
in 2nd gear. But yesterday after a 45-minute ride, it would only happen
once out of 3-4 tries at WOT. (I say engine oil because yesterday and
today, engine coolant was around 175F, but I'd guess that the oil hadn't
warmed to coolant temp after this morning's 15-minute ride but it probably
had after 45 minutes of riding yesterday.)
--When the slip/grip happens, it feels like the clutch is being
fanned. The RPM don't drop with a "bang".

Since it happens only in 2nd gear, I'm inclined to think that it's a problem with the transmission. On the other hand, I'm not exactly sure what could have failed in the trans to cause this. If it was worn shift dogs, I'd think that the trans would fall out of gear during the slip/grip or give me false neutrals during the 1st-2nd upshift. If it was a broken tooth, I'd think that the slip/grip would happen multiple times during 2nd gear runs. And I'd think that the grip part of the slip/grip would happen with a bang.

However, if it's not the clutch and it's not the 2nd gear teeth or shift dogs, what else could it be? Nothing I can think of. So maybe it is something in the trans.

[thefleshrocket]

Also check the clutch cylinder as it may have some crud built up on it not allowing the rod to fully disengage . It is a common problem with a bike this age .

I haven't done this yet and I'll be sure to do so. But.. how could the clutch slave cylinder cause my symptoms to occur? If the clutch wasn't engaging fully, wouldn't the problem be present in more than just second gear? And, wouldn't the symptoms be more like a worn clutch (engine RPM climbing faster than it should until I let off the throttle, rather than a quick "slip"?

[kaldek]

Is this slipping occurring immediately after an upshift, or seconds afterward? Like, if you change up and hover around 5,000rpm for a while then smack the throttle open, does it also happen then?

[spud786]

Also check the clutch cylinder as it may have some crud built up on it not allowing the rod to fully disengage . It is a common problem with a bike this age .

I haven't done this yet and I'll be sure to do so. But.. how could the clutch slave cylinder cause my symptoms to occur? If the clutch wasn't engaging fully, wouldn't the problem be present in more than just second gear? And, wouldn't the symptoms be more like a worn clutch (engine RPM climbing faster than it should until I let off the throttle, rather than a quick "slip"?

Generally when a clutch has mild slip issues in taller gears which stress the clutch more Espically up Big Hills, its usually sharp Jolts, that come and go.

But 2nd gear is normally a Balistic Launch gear, so it can see as much stress . The slave fluid, has to be done fairly often atleast the resoviors, to avoid flat out blockage in the orifices .