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« on: February 28, 2009, 05:26:41 am »
Here is some help from Bill Campbell from the Penton site :
I have owned a 74 and 76 250 since new. The 74 had the old square block brass? plates and the clutch began behaving badly after the first rebuild. I tried most of remedies. With gear oil the clutch would not disengage and I resorted to putting it into gear on the move. If I tried ATF the clutch would slip under load. I looked at the distance of the arm from the engine case but didn't really try too hard to change that.I put up with the dragging clutch for 30 years.
My 76 250 has the fibre plates with the swirl pattern. Not long after I purchased the bike I fried the clutch up a muddy hill. It starting grabbing and made it difficult to have any clutch control. I didn't make it to the top however the clutch action returned to normal the next time I rode the bike and has been that way ever since.So I have one bike with one type of clutch plate that was a complete pain and another that was and is as good as day one.
I rebuilt a 400 a couple of years ago that has the same plates as the 76 250 and that works very well. I have spent the last couple of year trolling ebay for some more fibre plates for my 74 250 but they are rare. I finally got a set and put them in the 74. Guess what? the bike now goes into gear whilst it is stationery and there is no slippage.Just like my other bikes.
My take on this once the crappy old rectangular plates get a little old they are less than useless and should be replaced with the swirl pattern fibre discs that in my experience are more forgiving.
Cheers Bill
PLus another bit for dial gauge setup :
Larry - Here's what I've done and it's helped a lot, on both KTM and Husky motors, which have almost identical clutch designs:
- If you don't have a good one, go buy a cheap dial indicator and if you can find a cheap one, a magnetic dial indicator holder with the fancy adjustable arms. Harbor Freight Tools sells adequate cheapos for about $10 each.
- Lay the bike on it's left side and pull the clutch cover off, oil will be drained off to the other side
- Pull in the clutch lever and velcro wrap/rubber band/bungie cord it off so it's pulled to "full disengaged"
- Set up the dial indicator so the tip is riding on the outside edge of the flat front of the pressure plate (pushed fully out due to the clutch pull) just outside the retaining nuts. I've stuck a bar clamp across the back of the cases in front of the carb, clamped the sides, and then stuck a woodshop spring clamp across the bar end sticking out to grab on to the dial indicator to hold it in about the right spot. A magnetic holder is easier.
- Then turn the motor over to see how out of "flat" the pressure plate is. Adjust the retaining nuts to get the fully opened pressure plate to ride as flat as possible in this open position. Then cotter-key or safety wire the nuts.
This, along with synthetic ATF in the tranny, has worked the best to minimize clutch drag down to acceptable levels, without the need to buy a new non-grooved clutch basket or new flat driven plates, etc. You may have a pressure plate that's warped or grooves in the basket fingers that prevent the plates from releasing easily. I've had the pressure plate read flat as a pancake without the lever pulled, and catty-whompass when disengaged out with the lever pulled---so important to check it with lever pulled.
Hope this helps.
Adrian
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