SOHC.co.uk Forums > CB750

Dragging clutch

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JezzaPeach:
I may be on the wrong tack as I’m visualising the 500/4 mechanism, but could it have the subtly wrong model of or worn lifting cam/lever bit/ball bearings?

Scottvincent:
Nurse Julie, I will give a mineral oil a try. I am supposing that back in the 70s, this is what Honda would have used? Any recommendations?

Thank you.

McCabe-Thiele (Ted):

--- Quote from: Scottvincent on January 06, 2021, 04:34:10 PM ---Nurse Julie, I will give a mineral oil a try. I am supposing that back in the 70s, this is what Honda would have used? Any recommendations?

Thank you.

--- End quote ---

I've read lots of advice about Synthetics & Semis not being suitable for older bikes - Exol do a semi synthetic suitable for wet clutches. I'm going to probably use the Asda Mineral Oil.

K2-K6:
Something odd with the clutch pack, and possibly it's "willingness" to sit flat when you assemble.

By tightening and not backing out the screw you effectively set the lift mech to touching the thrust bearing with no space, when you tried to use it the plates must have compacted more to then slip with it set like that. It moves the whole combined clutch plate pack toward the lift mech, which shouldn't happen.

Using it as you've set it now (after the pack has found a natural home point) will probably help and certainly allow you to asses it further. Gear changing won't change anything as such but clutch use to pull away etc will.

To make a problem statement,  the clutch mech lift is insufficient to make each plate run clear enough from it's neighbouring plates to prevent torque driving through them.
Ordinarily, a prime cause of that would be having bent or bowed plates. Are you certain that the plates are substantially flat (check on a piece of glass, for wave form and also for peripheral to internal diameter (making sure they are not cone shaped)  as any significant variance will take up space that can't be accessed by the lifter mechanism, and drive will always be in place as you have in dragging.

You can check them with feeler guages against a known flat surface.

philward:
I had a similar issue on my ZZR1100 but not as pronounced as your issue. I changed the steel plates and that cured it. I would check the steel plates (as K2 - K6 suggests) before just changing them though as they are expensive - and may not cure the problem.

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