CT90, auto-clutch not disengaging when shifting (lurching)

Discussion in 'CT90, CT110, ST70, ST90 Discussion' started by joel1234567, Apr 28, 2021.

  1. joel1234567

    joel1234567 New Member

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    Hi, I have a 1972 CT90 with a clutch that never seems to diengage. I've triple checked everything and scoured the interwebs and I've seen a number of people and posts with the same issue but never a resolution.

    When I shift it into 1st gear at idle, on the center stand, the rear wheel spins with some force, with the shift lever all the way down and when it returns to the up position. But the bigger issue is that when I press down and hold down on the shifter in any gear at speed it does not disengage the clutch, to allow it into neutral. I should be able to press and hold the shift lever and rev the throttle freely without any effect at the rear wheel but the clutch won't let go and instead it lurches into gear.

    I understand the mechanics of pressing the shift lever down, which rotates the cam plate up against that thing with the three balls, which then pushes the entire clutch housing inward to the point that the bob weights in there no longer contact the clutch plates, which should free up the clutch so that everything freely spins as long as the shift lever is held down. And the clutch has been adjusted by turning the adjustment screw counterclockwise until friction is felt then clockwise 1/8 turn and locking it down. But it all doesn't seem to be working right for reasons I cant figure out.

    I believe the clutch was assembled correctly, verified by off the bike it turns in one direction and locks in the other direction. The shift drum stopper arm and plate are also in good condition, no loose screws in the stopper plate or anything like that.

    From all that I can tell I'm the first person to go poking around in the right side of that engine so I don't think it's an assembly issue. All of the screws on the case were in good unstripped (but corroded) shape and it looked to have the factory gasket. When I got the bike, after getting it running, it was both lurching during shifting as described above, and slipping when kick starting it. I replaced the clutch pads and now it doesn't slip when kicking but it does continue to lurch when shifting.

    I found one post online where the poster had the same issue. They swapped out the clutch bell, but also the oil pump, and it corrected their issue. Would the oil pump have some bearing on this? I've put several miles on the bike and it hasn't seized up so I would think the pump was working, but maybe its not 100%? There was quite a bit of sludge internally at the bottom of the right side and on the filter screen which I cleaned out when I replaced the pads.

    Sorry I know thats maybe a heap of info to take in but just wanted to let folks know all that I've tried and considered and see if anyone else has any ideas. I suspect anyone that has dealt with these autoclutches may have some insight, CT90 or otherwise.

    Thanks!
     
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  3. b52bombardier1

    b52bombardier1 Well-Known Member

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    What type of engine oil are you using? It should be a "JASO MA" rating oil for use with wet clutch engines. This will be in the tiniest print on the back of the oil jug.

    Rick
     
  4. joel1234567

    joel1234567 New Member

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    Honda GN4 10W30
     
  5. OLD CT

    OLD CT Well-Known Member

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    I think it is just adjusted incorrect. Try turning it clockwise all the way, then counter clockwise until you feel resistance. Then a 1/8 turn clockwise.
     
  6. joel1234567

    joel1234567 New Member

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    Thanks. Have tried that after assembly. And have also tried it after having removed the RH cover, clockwise all the way. Then hang the tri ball thing on the adjuster and spring on the cam, then replacing the cover and then turning counter clockwise until resistance. Have tried backing it off 1/8 clockwise, no backing it off, and even a half turn and full turn counterclockwise past the point of resistance.
     
  7. kirrbby

    kirrbby Well-Known Member

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    Try this...
    Turn right till it's free...then back left to resistance...the go 1/4 or 1/2 turn farther LEFT.

    See what it does...
    Turning left, into the resistance, preloads the clutch pull off.
    If it's cured, it's cured. If it's better, you'll know you're on the right track. If it's worse, or the same...nothing lost.
     
  8. joel1234567

    joel1234567 New Member

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    Thanks for the suggestion. That's what I was trying to describe doing in my previous post.. apparently not very well :)

    "Have tried backing it off 1/8 clockwise, no backing it off, and even a half turn and full turn counterclockwise past the point of resistance."

    By counterclockwise I mean your "left", to preload it, like you were thinking. Same result.
    I'm with ya, good suggestion... it's just beyond all understanding I think at this point.

    Anyone have thoughts on the oil pump replacement? Would that have any bearing on the issue? I'm grasping at straws now.
     
  9. b52bombardier1

    b52bombardier1 Well-Known Member

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    The oil pump has nothing to do with it.

    Rick
     
  10. kirrbby

    kirrbby Well-Known Member

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    How about your idle speed...are the rpm's dropping down low... enough for the clutch to disengage?
     
  11. joel1234567

    joel1234567 New Member

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    Thanks for the reply kirrbby, I think I missed that one in my inbox. Idle speed was good.

    I had some success over the weekend. I've been reassembling by leaning the bike left, putting some grease on the tri bearing plate, and then sticking it to the inner cam plate. I put it together this way maybe 4 or 5 times and the clutch was not functioning properly. It rammed immediately into gear when the shift lever was pressed down, before letting it up, between all gears.

    I found a write up from the CT Shop (http://www.thectshop.com/index.php?p=1_10_Clutch-repair) with the recommendation to put the spring on the inner cam plate, and then hang the tri bearing plate on the side cover's adjustment shaft. With no lean in the bike, on center stand, I gave that a try with the side cover cam plate adjusted out to its farthest setting (screwed clockwise as far as the adjustment would go)

    Before tightening everything down again and filling (and wasting) more oil, I reassembled and just put in a few screws to hold it all in place. No oil this time. Rotated the clutch adjustment counterclockwise until resistance, then back 1/16 clockwise and tighten down.

    Up on the center stand I put it in neutral, rotated the rear wheel freely, pushed down and held down the shift lever... continue rotating the wheel, there was some additional resistance (more than when in neutral) but it could be moved fairly easily with a couple fingers. Then I let up on the shifter and tried to continue rotating the tire and it was more or less not moving (as I'd expect).

    Did this rear tire rotation/shift a few more times, adjusting the clutch a little in and out to feel the effects of the adjustments that I was making in the amount of resistant when I had the clutch lever pressed down and was moving the wheel. I could feel slight changes as I adjusted it so I was feeling confident that it was working now as expected. I have another working CT90 and I did this same test to verify the same sort of feel on a working bike, verifying that same little resistance feeling when the lever was down.

    Everything seemed good. Screwed it all down and filled it with oil and took it out for a test run. Ran like a champ, perfectly!

    So I guess it was an issue with reassembly of that tri bearing plate and side cover. When hanging it on the inner cam it must not have been lining up on the adjustment shaft properly when I put the side cover back on. That's all I can think of. That's the only thing I did differently. Might have been just off-center and getting pinched at the end of the adjustment shaft, between the end of the adjustment shaft and the inner cam plate? With all the number of times I had it apart and back together you'd think I'd have gotten a lucky alignment at least one of those times.

    I'm still not certain how it would have gotten into that state before I replaced the clutch. Perhaps the previous owner had it apart to look at things when the clutch was slipping. But there was no sign that I could see that anyone had ever touched those RH case screws or gasket. I wonder if you crank the adjustment shaft all the way in one direction if the tri bearing plate can shift off the end into misalignment? Seems unlikely.

    Sorry, another long-winded post again. Hopefully that might help someone in the future. I'll def be hanging the spring on the inner cam plate and tri ball pate on the adjustment shaft next time I do this. And I think the tire rotation test test with feeling for light resistance, but not fully engaged in gear, while pressing and holding down on the shift lever before getting everything re-assembled for a test run is a worthwhile test. If anything is out of whack or improperly assembled with the tri bearing plate you should be able to feel the rear wheel fully engage into gear unexpectedly when pushing down and holding the shift lever.
     
  12. kirrbby

    kirrbby Well-Known Member

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    If you were leaning the bike over...it's VERY possible the shift lever could have been hitting the floor...pushing it out of position...which would have you putting the clutch release lever in the wrong position...on the RIGHT end of the shift shaft. That is a common oversight when you lean the bike waay left to assemble the clutch release bits.
     
  13. joel1234567

    joel1234567 New Member

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    That's a good thought, I hadn't even considered to check. Just did a quick check but I don't think I had that extreme of a lean. I had it at about 45 degrees. I just leaned the bike over 45, there is still a good 6 inches+ to where that lever would touch the floor.
     
    kirrbby likes this.
  14. Clayton

    Clayton Active Member

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    I had the exact same problem on a CT70, I thought everything was perfect and guess what?!?! My assembly was wrong due to me leaning the bike to far over. I’m a rookie so I chalked it up to a rookie mistake lol.
     

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