CT 70 Hard to kick over. 3 speed auto. Any thoughts?

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Grouper

Member
I have a 1971 ct70 (that would be a K0, correct?) 3 speed auto. that only has around 700 original miles. Its been sitting for many many years. This bike does run, But when I kick the bike over I have to give it a hard kick to turn the motor over. If I give it a moderate kick, (still more than this little motor requires) there will be resistance and at the same time slippage, and the motor doesnt turn over. Im almost positive this is a cluctch/fluid issue of some sort, and not a mechanical problum.(like a stripped shaft, NOOOO!)

Has anybody expereinced this before? If you have, was it a simple adjustment? or maby Bad/wrong fluid(im assuming the motor oil lubes the clutch)
Hopefully someone can help me out, Im trying to get this bike ready for the road.
 
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b52bombardier1

Well-Known Member
Try adjusting the clutch first and it does not seem to be a shaft slippage issue. I have heard of some types of oil causing clutch problems - some synthetics are too slippery. Your clutch fiber disks might also be glazed.

But try a clutch adjustment first and see what happens.

Rick
 
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G

Grouper

Member
b52bombardier1 said:
Try adjusting the clutch first and it does not seem to be a shaft slippage issue. I have heard of some types of oil causing clutch problems - some synthetics are too slippery. Your clutch fiber disks might also be glazed.

But try a clutch adjustment first and see what happens.

Rick
Click to expand...

Thanks for the reply! Im glad you also dont think it sounds like a stripped shaft.
Could you enlighten me on the best way to adjust this clutch? And is there any test I can perform to see if my disks are glazed?
Thanks again!

edit: O yea, And what oil should I be putting in it, (I guess the motor oil does lube the clutch as well)? Can I use Cheepo Home Hardware brand 10w-30, or is it special oil for some reason?
 
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darrel gunderson

darrel gunderson

Active Member
Do yourself a favor and do NOT run car oil in that engine. In fact I think you should get it running and drain it to be sure. Car oil is too slippery and could be the cause of the slipping you are having. Only run motorcycle oil made for wet clutch's. 20-50wt is what I recommend.

Darrel
 
6

69ST

Well-Known Member
Not only can automotive oil cause clutch slippage (especially synthetic), it lacks ZnDDP - a zinc-based, high film strength, lubricant that protects flat tappet cams, in car engines...and the tranny in bike engines. 20W50 GN4 oil is my personal preference. Bear in mind the fact that this is thick oil and warm-up the motor thoroughly before hammering it.
 
busa

busa

Member
I had the same problem and clutch adjustment fixed the problem. My service manual said to adjust the clutch backward from the YouTube video but the video was the correct way.
 
zorgitron

zorgitron

Member
Car oil is too slippery? Oh man... I ran cheap 10w-40 car oil in my C70, KLR250 and my current 88 build. It seems ok, but am I slowly wrecking everything?
 
G

Grouper

Member
Its been a little while since the original post. I have adjusted the clutch like the video says. But I have not had a chance to change the oil yet. After the clutch adjustment it seems better. But now it doesnt it in consistantly. sometimes it kicks the motor over, sometimes it slips with resistance. Probly the oil do you think?
Thanks Guys!
 
OLD CT

OLD CT

Well-Known Member
Your best bet is to freshen the engine up,low top speed ''30'' and your clutch slipping makes me think it's time to go over the top end and rebuild the clutch for sure.Fiber plates and new springs.Need to buy some ct specific tools too.And a good time start running bike with wet clutch only oil after your overhaul.
 
Gary

Gary

Well-Known Member
Back in the days of mine being new all we had was car oil. Oil has come a long way since. When I started using them again a number of years ago,before ZDDP issues,I used car oil again. Started having clutch sticking issues,after a couple of days of non use I would have to bump start it and ride around a bit with the clutch in to get it free,kind of hard on it too. Changed to Honda oil and have had no trouble since. Of all these MR 250,TL125,CT70H,Z50,XR70 the TL and the H were the most affected. H plates had been replaced, the TL are original Honda. Since then I have only used Valvoline 4 stroke and Honda oil.
 
G

Grouper

Member
Just an update guys! Ive changed out the old unknown oil for the penzoil 20-50 motorcycle oil. I re ajusted the clutch by completly removing the lock nut, spining the screw clockwise about 3 complete turns untill finally there was NO resistance. I then turned it back counter clockwise untill i just left resistance, then turned it clockwise again about 1/8 a turn, and held the screw tight while I re installed and tightend the lock nut.
This seemed to fix the problum so I thought, But after a 30K ride breaking in my new rings, I did notice the clutch sticking a couple times when I kick started it along that ride. It also seemed like it slipped a bit more off the line, Like I had to rev it up louder to get going..... (possibly I was just concious of the loud little tailpipe at 1AM and the "slipping" off the line was in my head). But on the ride it shifted fine, NO slipping up hills, I could even lock up the rear wheel if I down shifted to soon! So I guess its pretty unlikely theres accesive clutch slippage from a stand still. What do you guys think?



Since I hit about 30K on the fresh rings, last night I started to change the oil, I also pulled the clutch cover off and found a HUGE amount of crud built up in there! Theres 3 or 4 groves in the inner clutch hole that I didnt even know excisted because there was so much junk built up around them it just looked like a smooth black circle, untill I wiped it with a cloth a realized how thick the goo was! WOW!
Im going to throw it back togeather today, cleaned up with fresh oil and I am wondering If I should inspect the clutch befor I put it back togeater? If I should, How do I do that!??
Thanks Guys!
 
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6

69ST

Well-Known Member
You've discovered the reason why I keep harping on cleaning-out the oil spinner. It does a pretty good job of trapping clutch wear debris...and break-in debris...which is why the owners manual recommends the first cleaning at 300 miles. No one ever did this when the bikes were relatively new, the spinner chambers filled, grit circulated throughout the engine and, voila!, lots of engines in need of rebuilding after very few miles.

Automotive oil was fine, until ZNDDP was removed and synthetics became available. It's the worst of everything...tough on shift forks & gears, good chance of clutch slippage. At this stage of your project, I absolutely would pull the clutch for dis-assembly, cleaning & inspection. I'd also replace the friction discs, they're inexpensive. If you can still see the dimples in the steel clutch plate faces, they're fine; otherwise, check the thickness against specs or just replace them. If your clutch has two single-sided friction discs, plus one that's double-sided, you'll be replacing two of the plates anyway. This usually cures the slipping problem, even with the vintage original springs reused. New springs are cheap, too. Just run bike oil, formulated for use with wet clutches, and your rebuilt clutch will be fine.

Only additional special tool you need, from this point, is a clutch nut socket.
 
Tori

Tori

Member
Great info. My '78 has been doing the same thing, and i've tried all of the above. Guess it's time for a tear down.
 
OLD CT

OLD CT

Well-Known Member
I always use new clutch springs,40 years is enough time for them.One bike didn't need fibers or plates just springs to cure the occaisional slip when trying to start the bike.
 
6

69ST

Well-Known Member
OLD CT said:
I always use new clutch springs,40 years is enough time for them.One bike didn't need fibers or plates just springs to cure the occasional slip when trying to start the bike.
Click to expand...
Good points, OC, they can have varying amounts & causes of slippage, one engine to the next. I, too, have run across a few examples of exactly what you mentioned. And, replacing 40-year-old clutch springs is sound practice. With any motor build beyond the stock 72cc tune, especially with a manual clutch, not replacing the springs is begging for clutch slip. That said, I've also seen slippage with new discs, plates & springs, particularly when cold, until the friction material had a chance to bed-in.

Yesterday, I rebuilt the clutch in a well-maintained `76 with 3100 original miles. The oil spinner had obviously been serviced, compression was 150psi cold, the motor easily pulled to 40mph and was still climbing. I'm not yet 100%, "bet-the-farm" certain that automotive oil was the cause, even though a new set of discs was all it needed. The previous owner had sanded the plates, 120-grit scratches were still fresh. The friction material itself wasn't heavily worn, or burnt; it did, however, feel more like circuit board than friction material. Judging by the shadetree clutch "refresh" and the amount of gasket sealer slopped over the torn clutch cover gasket, automotive oil seems the likely problem.

Contaminated friction discs oftentimes must be replaced to correct the slippage, but that's all it takes. A number of EU riders have experienced this when running synthetic oil, as well as ring-seating issues. I suspect that wet clutch compatible synth would be no problem, I'm just too cheap to experiment. Plus, imo, you'll get more value from two oil changes than running the more expensive oil twice as many miles. As for the ring-seating, many have claimed that problems can be avoided by running the more conventional dinosaur juice for the first 1000 miles.
 
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