I have been going at MY clutch drag problem all Summer long, and although I do seem to be gaining on it I am STILL having issues.
I have a '99 400 that has the sweetest clutch I have ever had on ANY dirt scoot, or street bike for that matter, but unfortunately that year has no button on it so it has been turned into a DS bike cause I hate kicking em over all day out in the woods even though it starts first kick every time. We spend a LOT of time clearing and maintaining trails so LOTS of restarts, and I NEED a button!
I am very surprised at what a GIANT leap backwards my '03 450 clutch is from the '99!
I have checked all the plates and they are all good, flat, no burning, and look near new. The bike only has about 2500 miles on it.
First attempt I tried the washers. They seemed to help while in the garage but once on the trail were a big FAIL! Creeps when in gear, keeps pulling at slow speeds when you pull clutch in and that sucks on tight knarly trails. Also real hard to find neutral. You can get it if you blip the throttle, but my real issue is the drag.
Next, I tried replacing the judder spring and seat (which fit inside the innermost narrow cross section clutch plate) with a new full size clutch plate. This is how the YZ's of the same year are done. Not much change and when in the wet or rain you could feel it do this weird slip/judder on takeoffs. I opened it up again and tried adding YZ springs which really made it a LOT harder to pull and that wore my hand out PDQ. By about noon it was starting to cramp.Still did not cure the drag either.
Next, I went into the clutch boss (innermost hub on the clutch) and noticed the six inner holes on the backside that allow the oil into the boss were really nasty looking holes with a lot of casting flash (burrs) built up around them. They are sort of strange holes in that only half the diameter of the drill point breaks through when they are machined but I figured that flash needed to be cleaned out so spent about an hour with an itty bitty file and opened and smoothed em out....figured a little more flow of oil might help. WRONG, no change.
Next, I opened up the six holes that allow the oil to flow out of the boss onto the plates by fifteen thousandths (.015) I believe that calculated out to about 28 % more area which should flow quite a bit more oil. I have seen where they do this to the 250's and quite a few people rave about the results.We rode the next day in rain and it was a failure as well. Kept stalling the bike going DOWNHILL when I would pull the clutch in. Turned idle way up and that helped some but clutch would still drag at all slower speeds.
Next, I picked up a used low mileage clutch off e-bay, so I took the boss on it, filed out the flash on the inlet holes and left the six outer holes stock size (.113) but added six more holes, same size in the same plane/rib as the six that were originally drilled into that boss. You want to keep them in the same plane as on the inside of the clutch boss there is a rib that catches the oil as it enters and directs it out a little channel cast in the boss to the outlet holes. I also noticed that these six holes do not allow for hardly any oil to flow through to the outer 3-4 plates. Therefore I added three of the new six holes out near the outer front edge of the clutch boss. BIG DIFFERENCE! It still wants to creep a little, and will pull slightly when throttle shut off, but now goes into neutral real easy! Making some headway.
Today I did some measuring on the clutch that is not in the bike checking out the YZ vs. WR springs.The compressed length of the springs (both YZ and WR) when installed in the clutch is right at One Inch, 130 thousandths. (1.130"). The WR springs appear to have enough clearance between the coils that they can compress enough when the clutch is pulled in and that there will be no coil binding but the YZ springs might not have enough clearance, and that could have been why my hand was getting so tired when I tried them as they ARE very close to coil binding.The YZ's have a different wind and spacing than the WR's and that extra length and spaces between windings does makes a difference and use's up some room.
I may try the washers again with the WR springs as now I am starting to think due to the way it now feels that some of the problem might be when the clutch is pulled in it needs more room between the plates to allow the oil to escape faster from between them. I think now I am feeling a sort of a hydraulic drag due to the oil not escaping from between the plates quick enough when clutch is pulled in. This to me would explain why the drag lets up some when throttle is blipped while in gear and at a stop with clutch in, or how a higher idle makes the drag less.The washer trick only gains a tiny amount though as the washers are about .060 thick and then you have to divide that by seventeen plates.
Will update once I know more.
Most people would have just sold the bike....but I am not much of a quitter!
Sorry this turned into such a novel.