I've been having some fun with my clutch recently and wanted to share my solution, as I've read a lot about these two issues in the forum and haven't seen this one.
I bought my CB750 K7 a month ago, not running, and have been fixing it up. Last week the clutch started to slip; I recently changed the oil to 10W40 Silkolene, put on a new clutch cable, overhauled the carbies and tuned the motor. Based on answers on SOHC I thought it could be:
- the oil
- cable adjustment
- engine finally putting enough torque through to make the clutch slip, ie need new springs or plates.
I went through the adjustment procedure; the adjustment screw inside the locknut on the clutch basked was screwed in too far (should be backed off 1/4 turn from where it makes contact), so the clutch wasn't being allowed to engage fully. Problem solved right?
Nope...
Now the bike wouldn't go into neutral at rest, with the engine running. Likely cause? Clutch drag, ie the adjustment that fixed clutch slip now meant that I was going the other way, and the clutch wasn't fully disengaging.
So, what to do? If I adjusted the clutch in, it would slip, and if I adjusted it out, I couldn't get neutral. Cable had the right amount of freeplay, adjustment on the clutch basket was right. Then I had my "aha" moment...
The lever was a bit loose; not freeplay loose, but wobbly loose. I pulled the lever and sure enough, the hole where the lever pivots was not round, but oval shaped. Clearly over the last 35 years that poor little piece of aluminium has been worn away. The result is that if you adjust the lever to get enough freeplay, you can't pull it in far enough to fully disengage the clutch when it's touching the handlebar grip.
Solution? Temporarily, put a small piece of cable tie, nicely rounded and chamfered, into the gap to round out the pivot hole. Longer term, buy a new lever or make a brass insert. Either way the clutch now engages and disengages beautifully!
