Rookie Clutch Question - ISDTRR Prep

[LarryVolenec]

I have been reading all the previous posts on clutches and the actuator mechanism and the Penton Shop Manual in an effort to try to resolve a clutch drag problem (clutch will not fully disengaged then clutch lever pulled in) prior to the ISDTRR in Tulsa on a 1974.5 Penton 250 Hare Scrambler.

The clutch actuator arm had a bad wobble, so I purchased the kit from Al and rebuilt the actuator mechanism.  I installed the new domed end replacement rod, the new 6mm ball, the existing second rod, and then the actuator mechanism.   I am trying to measure the distance "0" from the inside curve of the actuator arm to the engine to see if it is now in spec and if not, to determine if I need to add a ball and cut down the rod.  

The picture in the manual is a little confusing on where the measurement is taken on engine side and there appear to be three possibilities (tough to describe in words to please bear with me).

1. The flat area on the actuator mechanism just above the top stud, washer, and nut which attaches the actuator mechanism to the engine case.

2. The raised edge of case at the top of the case where the edge around the a full magneto cover comes in contact with the engine case.

3. The flat area on the engine case between the mounting pad for the actuator arm and the raised edge of the case at the top of the engine where the edge around the magneto cover comes in contact with the engine case.

Thanks in advance for any and all help provided!

Larry Volenec
Daytona Beach, FL
[email protected]

[tofriedel]

Larry,

In Looking at my manual, I believe your #1 solution is the correct one.

Based on the information in "Keeping Track" August 1974, "Let's Do It Right" column, clutch drag was a problem on the 250's, especially the earlier ones.  The solution was to go through the throw out system to insure full clutch disengagement.  Then use automatic transmission fluid (ATF).

Tony Friedel

[Big Mac]

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.

[LarryVolenec]

I appreciate the suggestions and will definitely give them a try.  I have a dial indicator that mounts to a modified set of vise grips and that should do the trick nicely.

Thanks again for the replys.

Larry Volenec

[chicagojerry]

larry, i sent you an email off-line drop me a note back if you like. chi jer

[Bill Campbell]

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

[slvrbrdfxr]

Larry,
I just went through this same scenerio myself. I fought a dragging clutch while riding my 77 250 GS6 at the 2007 ISDT RR and at the CC race at Mid Ohio. It wasn't too bad at the start but got progressively worst the longer I rode due to the heat build up in the clutch. It got so bad at one point at Mid Ohio that I could hardly even pull the clutch lever in. I finally got it solved last month. After reading the previous posts I agree with all of them. Big Mac's clutch set up method should work fine provided the plates are not warped. You'll have to take your clutch apart and check all the pieces on a surface plate and then toss out the disc/plates which are out of tolorance or marginal. Bill indicated he switched to the fiber clutch plates and thats the same thing I ended up doing to solve my trouble. Tony suggested using ATF which is right on the money. Bottom line in my book now is to use the fiber discs if avaialable instead of the sintered copper and set it up as Big Mac suggested. Hope this helps. Talk to you later.
Dave McCullough

[LarryVolenec]

Thanks again for all the suggestions.  I checked the run out and got it to .002". The plates are sintered copper so I will be looking after the ISDTRR to replace them with the fiber ones (if I can find them). Also filled the transmission with ATF Type F.  

Have a few more tasks to do before I can run it this weekend.

I really appreciate the tips.  I have printed them out and they are now is a clear plastic sleeve in my shop manual.

Larry