Race Report, Mason County MX May 13 - Clutch issues

[robwbright]

(This is a long one which references the clutch isue I have been having.)

I guess I should have known better than to race on the 13th. LOL

I spent awhile Saturday afternoon re-installing my clutch. The basket had been notched - which I filed - and I found that there was a fiber plate missing because the aftermarkets the previous owner had installed were too thick.

The plates all looked good, so I tried just adding an OEM fiber. It made the stack too tall and I could not get it to work at all that way. I put it back together with 7 fibers, 7 steels and tightened everything down.

I was a bit concerned about the nut which holds the inner hub - I don't have the proper tool to hold the hub and I had some difficulty holding everything so I could tighten the nut. I was (almost) satisfied and bent the lock washer over. It was getting close to race time and I wanted to get going. Neither my dad nor my father-in-law were available to assist. Finished the job, put in the oil, everything seemed fine, and the clutch worked as well or better than it had since I got the bike.

Went to the races at 4:00.

Practice was fine - it was great to have a clutch that worked again. In the heat we had 11 bikes. Open class. I started in 4th, passed one guy, 2nd place washed out in a downhill right hander, and I was 50 feet behind 1st. Unbeknownst to me, he was a pro until 98 and then quit riding. He was back out there on a 95 KX125 for his 3rd race back. I couldn't catch him.

I made my gate pick and got a decent start - 3rd, I think. I passed for 2nd in the second corner and things were looking good because the ex pro was behind me. However, a 450f passed me in a corner and I was a bit surprised because I had beat him easily in the heat. I was staying right on his tail into the 2nd lap.

(Interesting note: The top 3 bikes in the heat were a stock 125, my 144 and a near stock 125. Of the other 8 bikes, 6 were 450f's and 250f's.)

I grabbed for some clutch exiting a corner and there was nothing there. The lever was there, but no tension whatsoever. Next corner, same thing. Needless to say, I was ticked and worried. However, I was running 3rd, not losing any time and not close to being passed. I thought I'd try to finish it if I could - or until I heard something bad from the motor.

Maintained 3rd until the 2nd corner of the last lap - a 180 left hander. I tried a tight inside line to try and pass the 450f. Went to 1st gear for a lot of drive out the the inside line and the motor stalled. :bang:

No clutch, so I had to struggle with trying to find neutral - and I'm not very tall, so it was kind of difficult in the somewhat banked corner.

By the time I got it restarted, I was in 7th. I finished the race rather PO'ed and worried about the bottom end.

Checked the cable - still hooked up and not broken. The motor did not seem hot, although on the last lap I had heard a noise coming out of the clutch side of the case.

Took it to dad's last night and tore the clutch apart expecting severe damage. Turns out I had either not tightened the inner hub nut enough, or I had not bent the washer over enough. The nut had loosened up - but had not come off the shaft. Whew!

Everything looked fine in there - no shavings, nothing bent, the bearings all rolled smoothly. I put it all back together, making sure to get the nut tight and the washer bent over completely covering one face of the nut.

Started the bike up and the clutch worked fine again. Again, Whew!

I plan to get 7 more OEM plates as soon as I can and rebuild the clutch.

 

[ecy063]

Sounds like you got lucky. I would buy a new nut, the old one might have been tramutized.

 

[HajiWasAPunk]

I don't know squat about the mechanics, but I'd have been freaked out to run it without the right number of plates?

I don't know if you have an impact wrench, but that's the only way to go for taking that nug off the clutch plates. I tried to do it without one and tore up the pressure plate and made a 40 minute job take 5 days (waiting on the part, because apparently no one in our county has ever bought one of these lol).

 

[robwbright]

I don't know squat about the mechanics, but I'd have been freaked out to run it without the right number of plates?

From what I've gathered, the key issue in the clutch is the overall thickness of the stack, not so much the number of plates.

As noted, the stack was too tall with 8 fibers, and the clutch wouldn't work at all. It's worked reasonably well with 7 fibers for a year.

My father in law has run an auto transmission shop for 25 years, and he also races a 125 Kart, so when he told me it was ok, I wasn't concerned about the thickness.

The cause of the lack of a plate is that the prior owner bought aftermarket plates that were too thick - thus he had no choice but to either leave one out or buy all new clutch plates.

Since the steels lock up on the inner hub, apparently I can have two steels together without slippage.