I’m trying to nail down the cause of my clutch pulsation felt while pulling away from a stop. ’08 SMR 510 with 7000 miles. Not the original owner. I’ve pulled the pressure plate and inspected the discs. The fibers were several thousandths away from the manual recommended minimum. Not sure what the steels should be. One concern is the inner basket, or hub, measured a 0.004 runout on the back surface where the first disc sits against. Any idea if this may be excessive? I have this question on another site as well and someone asked if the hub was tight. I’ll have to check that when I get home tonight.
I haven't looked up the min specs on this bike- but had the same issue on my ktm and dealt with it. From your discription- I called that a "grabby clutch" this can be from 1 or a combination of issues adding up to the result of what you have for clutch feel. Sounds like you verified that your friction discs are under minimum specs- so this makes buying new a bit of a no brainer- The decacreased thickness of the frictions can lead to slippage leading to more heat and possible warping of the steel discs. THAT in and of itself can cause a grabby clutch. Also if you inspect the basket and hub and see knotches or grooves where the plates float- that can cause grabbyness. I'd inspect further- and see if you can find min specs on the rest- I'd replace all discs and steels with new OEM parts- maybe springs. But check out the hub and basket. If you replace your clutchpack and the problem goes away- your good- sounds like you need it anyway... for what its worth... that's how I'd go about it.
if the frictions/discs are worn it'll slip, are they thinner or thicker than min? i assume they are on the thicker side as there's no slip complaint. if the fingers are notched excessively that'll usually cause it to creep at a light with the lever in and/or make it hard/impossible to find neutral due to dragging. dont file those down. leave them be or replace the assbly. i dont understand yer .004" rounout thingy...exactly how did you measure it on the bike and with what? i can't make sense of that one. sorry. my TC squaks and is choppy the first time i take off if the oil's cold. (hydro clutch) doubt that's the same issue yer having. "pulsating"? do it all the time and with any type of oil? hmmm...give george @ uptite a call. aint nothin' he dont know.
Used a dial indicator measuring the rear surface of the hub where the most inner fiber disc makes contact. Spun the hub and measured the amount that surface moves towards and away from the clutch pack. Should be flat but I'm not sure how much is acceptable. Surely this causes pulsing but I'm not sure if 4 thousandths can be felt??
.004". hmm...that could be total runout or warpage from point a-b. i dont know the service limits on this or if its even super critical. i'd be more concerned with vibraton if it was wobbly. my smr 510 had a pretty smooth clutch when it was warm, TC does too. forogt what oil i was using in the smr. call george @ uptite. grabby clutches can be caused by many things. if anyone can diagnose an issue over the phone he can.
ok i went back into some of my notes as this one sounds familiar but couldnt find anything. i think these issues stem from the clutch pushrod ends being oblonged, the lifter having wear and the basket needing a few holes drilled in the back to stop the pulsating/chattering/allow more oil in. i think this was done to a DR or an XR. if i recall i replaced the rod, lifter and drilled some holes in the back of the basket but....this one really has me scrathing my head so, wish i could get more on this but it was a long time ago. maybe i should call george lol.
The run-out of the Hub is not found in the manual- I would think someone such as George would know for sure what would be significant in terms of tolerances off the top of his head. .004” runnout at the Hub may not be a lot but if you consider that that the plates are not supposed to be warped more than .00078” that .004” sounds fairly significant. “Check the distortion of each plate (both lined and unlined) by resting on a flatsurface; use a feeler gauge.Wear limit: 0,2 mm (0.00078 in.).” [manual excerpt] I would check your plates again- I would expect them to warp Far before the hub. But it could be both. Like I said I don’t know the Run-out limit of the hub- just making guesses from what limits are expressed in the manual. I remember something along the lines of what PVDuke is talking about but I thought that had more to do with gear shifts and finding neutral than a dragging clutch feel.(just going by vague memory myself as well) But those can also go hand in hand- one symptom being more pronounced than the other... But it does make sense if the clutch rod is oblong at ends or bent and spins…
im kinda suspect on that runout mesurement. would be hard to get an accurate reading unless it was chucked in a mill and the indicator was mounted rock solid. unless it was id chalk up .004" to margin of error. if the ends of the rod/lifter aint perfect they can cause the lever to throb. if i recall correctly replacing the lifters and rod usually cleared things up if everything else was within spec. cc: cant find neutral, drags at stops. diag: notched basket fingers. i've done basket mods w/ the expressed understanding that removing any metal from the fingers can result in failure and actually make things worse. if one were to mod a basket (file fingers down smooth to remove notches) a diff friction/disc plate should be substitued with larger tabs to compensate for the larger gap. i dont do this hybrid basket work anymore, esp on a big 4T. too many liabilites. i tell the owner new parts only now or reuse the basket if the notches aint too deep. notching of baskets is a fact of life happens to most or all sooner or later.
Sorry guys, I probably stated the problem a little wrong. It's not actually felt at the clutch lever, it's the bike itself. Lurching on launch. So I think the pushrod idea would be just a feeling back to the clutch lever.... right? On another note, I don't have a socket on hand to check the torque on the clutch nut but just grabbing the hub and basket and giving them a good tug, I felt some play in the basket itself. That was from a rocking motion if that makes sense. Is that normal? Does it ride on a bushing and is some play expected? The hub felt tight. As for the .004 runout measurement, I'm confident it's an accurate measurement and could be repeated. With each turn of the hub, the dial indicator would repeat the numbers from the previous rotation.
I don't think you'd Feel anything at the lever from any of these suggestions. The result would be the lack of smooth clutch work in and out- with the results being how power is regulated from the motor to the wheel. (lurching as stated) not sure about the basket play described but doesn't sound right.
