this clutch has me stumped

[beechfront]

clutch has been slipping under full throttle for awhile now... so i ordered new plates.

they just showed up so i tore the old ones out. to my surprise the thickenss is the same. in fact, the old ones sometimes measure thicker than the new.

i swear i had that clutch adjusted properly. it was working fine for the longest time, then on my way home from a 1000+ mile trip is when it started slipping. tried to adjust again twice after that and it got no better.




measurements from old: .117-.119

measurements from new: .1165 - .1185

measurements from old metal plate: .0785 - .079

[chevy45412001]

slipper

double check that your clutch cable is operating smotlhly.I thought the same as you,at one time turned out being clutch cable.It would not fully disengage it was real sticky i couldn't even pull it back and forth when it was disconected. Some thing to think about.I put on a new one man it's like a new machine.

[pgg]

Large pressure plate is worn. Put in an extra steel plate to compensate.

[Ken Talbot]

Are you still running regular dino juice? Synthetic oil, or any oil with friction modifiers, can give you clutch slippage problems too.....

[rover]

Years ago, I thought my 79 SF clutch was slipping. When I wound it out, there was a point in the higher revs that the exhaust got louder, intake noise increased, and it felt like an auto trans kicking down. So at 40 mph in 5th gear, cracked throttle, pulled in clutch and released it. Instantaneous engagement. This had me stumped for over a year, but caused no apparent problems. Later, carbs started leaking. Took them apart, and found diaphrams all bad, so I used the carbs off the parts bike. About the same thing at high revs. One sleepless night, I got to thinking about this, and came to the conclusion that at the higher revs, there finally was enough vaccuum to lift the bad diaphrams all the way, opening the carbs properly, and feeling what seemed to be a slight gear change, and increase in power. So I pulled the parts bike carbs and checked diaphrams. BAD. Have since rebuilt the original carbs w/NOS diaphrams, and problem solved. I have 97,000 on the original clutch, and no sign of slipping. Just a thought.

[young nip]

clutch

Rover,
Funny my 79f does the trany thing in 5th at full throttle. when I back off the throttle it feels like it dropping into an over drive gear. im not sure if the clutch slips a little at that load the grabs when i back off. I dont feel any slippage when rolling through the rpms. Gets me there fast. my carbs should be top notch. Got me a good tech guru.Any ideas how much life is left inthis clutch? When my clutch starts feeling a slight mushy I know i need an oil change. about 2000k. Drop in a fresh sump Of castrol 2050 and it feels stiffer and engages smoother and its bang on .I check adjustment once a year.70ooo k on the bike. guess one of these years I should do a refit to the clutch.I suppose if it works fine dont mess withit?
Steve

[rover]

If you want to check your diaphrams, take off the seat, gastank. Then you can get at the carb tops. CAREFULLY take off the tops and look closely at the diaphrams. There should be no holes or tears in them. If there are, you found your problem. To check the clutch for slippage, go about 30-40 mph, and with full throttle, hit the clutch lever and quickly release it. If it grabs quickly, clutch is fine. If it takes a few seconds for it to grab, it is wearing. I used to run Castrol auto oil in mine, and wore out the trans main shaft bearing. Now I use yamalube, but a pal said his clutch slipped with that oil. Motorcycle oil is formulated to provide better lube for trans gears and bearings, auto oil is not. Our bikes use engine oil for the trans and clutch. This is my opinion after searching statistics on oils. Hope this helps

[beechfront]

well i am 100% sure it is slipping. just not sure why.

i asked my dad over the weekend, and he said that sometimes clutch plates can get glazed over and not engage properly. even though they are proper thickness.

i'm currently castrol part sythetic. i tried straight dino the last time and it did not help.

i think i'm just gonna put this sucker back together with new plates & springs.

after thinking about it more... i just have a sneaking suspision that it's the clutch cable. what does one of those cost anyway?
i need a new throttle cable too... gets pretty sticky when it's cold out.

i need to get this sucker put back together....

[John]

Why the cable? Is it too short? Is it not routed properly? The only thing that can happen to the cable is stretching, and breaking, not shrinking. They are still available. Have you checked the adjustment at the lever, and the adjusting mechanism where the cable attaches inside the cover plate?

[chevy45412001]

beg to differ

Sorry John your far off on that thinking.As i posted above,my clutch cable got real sticky inside the sheath(i never lubed it ) the cable would not fully release when you let it out.The spring inside the right cover was not strong enough to pull it through the sheath.When i removed the cable from my bike i tied to move it back and forth,forget it the cable could not be moved by hand.A member here on this site got me privy to that fix.And that was my clutch slipping problem.cables are readily available any where.bike shop on line etc. Got mine from bike shop for14 dollars.As for throttle cable ,just put one on three days ago.Got it on ebay for $10.90 that was with shipping.Seems to be a good part so far,again whole new machine with those two cables on new. clutch works better than ever so does throttle,good luck,and thanks to I think it was ratbyk for the clutch diagnosis.

[John]

Your right, Bigblock. I hadn't thought of the cable sticking inside the sheath. I've never had that problem, so it didn't occur to me. I've been wrong before, and it will happen again...more often that I would like.

[Ken Talbot]

Another thought - if the cable is adjusted so tight that there is no slack at the lever, it is possible that moving the handlebars could pull on the clutch and cause it to disengage. I've seen this happen moe often with throttle cables, on a bike blonging to a co-worker. In his case, it looks like the previous owner did not know how to adjust the clutch, so just did it with the cable slack adjuster.
JAT....

[beechfront]

i am sure i have everything adjusted properly. been through all of that a few times.

chevy454 - what you said would make sense. in the two years i have had the bike, i have never lubed the clutch or throttle cables. and judging from the fact that the throttle cable sticks when it gets cold - tells me the PO did not either and the clutch is likely the same.

will let you know when i find out for sure - and thanks for all the suggestions.

[chevy45412001]

cable adjustment

Ken also brings up a good point.I had no idea how to adjust cable at first,i did it by the bar end also.Then when i learned how to do it right ,i still didn't do it right.Forgot to back off the set screw when i had light contact,talk about getting po'ed with one's self.Since though i am running with an extra steel plate in mine,all my other parts must be wore enough ,cause i still had slip prob's with all else corrected.But now she's up to snuff and runs real fine.(Hay i for 1 know i'm not perfect either,i love that ole saying....$hit happens,least i can blame it on a horses droppings....lol)

[beechfront]

another strange occurrance...

this may sound very odd... at least to me it did.

but i noticed when accelerating over bumps it would cause slippage as well. this would happen at lower rpms.

example - when slowing down for a red light that would turn green, i would goose it and while going over the bumps the clutch would seem to break loose a bit. the only thing i can think of is that the rear wheel would maybe lose contact with the ground very briefly - causing the clutch to break loose when the tire grabbed again.


as far as the clutch cable adjustment goes - it's just fine.


those of you that have put the extra plate in there-- which side do you put it on? and have you had good luck with it? i just don't see that there is room for it.

also has anyone heard of clutch plates 'glazing over' as i mentioned above?