Dragging clutch

[Scottvincent]

I took a punt on a non-running 1976 F1 for not a lot of money. I worked through the bike and now it runs, stops and generally does everything reasonably expected of it except for the clutch. When I bought it, I assumed that the plates were stuck and that a good ride would clear things and when there was no change I removed the clutch and checked and cleaned everything. There was no change. The bike would only go into gear with a nasty clunk and the bike had to be held on the brakes, eventually stalling. At this point, I put it away and concentrated on the bikes that were behaving themselves! When the pain had subsided, I bought a new set of plates from D Siver and fitted them; again no change. The bike was banished again. Recently I had time to look at it again. Everything seems to be correct. The clutch action is smooth and the  cable is adjusted as per the manual but it still will not go into gear without a clunk and it drags badly. I have tried screwing in the clutch release by half a turn but it still clunks but not as badly. Can I turn the clutch release in further? ( I don’t really like to do this as I feel that it should work as per the book). Any suggestions would be gratefully received, as I have now had the bike for two years and I would like to ride it when the world returns to normality.

Thank you

[robvangulik]

By how much did you adjust the clutch center bolt (is that what you mean by clutch release?)
Normally it is screwed in until resistance is felt and than back a quarter to (maximal) a half turn. When you write you screwed it in a further half turn I think you had it far too much turned out!

[Nurse Julie]

Don't you mean screw the clutch release out further not in. Turn it in until it just touches then back it off  ¼ of a turn. I think that's the part in the manual with a miss print.

[MrDavo]

If I remember rightly, the direction arrow in the CB750 owners manual points the wrong way, at least it did in mine.

Like you, apparently, I learned this the hard way. 

[Scottvincent]

Thanks for the prompt replies but I must not have expressed myself accurately enough. I did adjust the clutch as per the manual, turn clockwise until it touches and then back off. At that setting, it will not allow me to select a gear without more crunching than my mechanical sympathy would take and then the bike will take off or will stall if I use the brake! I turned the adjuster screw half a turn extra clockwise to see if this would allow me to select a gear without the above happening. It almost feels as though there are too many clutch plates!
When I had the clutch apart I ‘dressed’ the slots in the clutch basket to reduce friction and I have changed from semi-synthetic oil to GTX to see if that had an effect.

[Nurse Julie]

Did your replacement clutch kit have the same amount of plates of the same thickness and did you replace them in the same order and are all the metal plates facing in the same direction, ie bevelled edge all facing outwards or all facing inwards?

[Scottvincent]

Thanks for the response. Yes, I fitted the clutch in same order, bevels the same way. The symptoms were the same with the clutch when I bought the bike, as when I replaced the clutch with the new one. I also replaced the springs.

[K2-K6]

Are you adjusting the clutch arm without the cable connected? 

It's easier to do as above to set the clearance. It should end up with the cable and arm about 90 degree to each other when the clutch lever is fully pulled in to the bar after setting it correctly. 

With the cable disconnected the  clutch end lever should have about a mm or two free play at the end of that lever if you move it against it's spring.  This would just about give clearance between the internal mech and starting to lift the plates, which then should be enough to lift the plates clear from the travel built into to lift cams.

[Scottvincent]

Hi
Thanks for replying. Yes, I do not think that adjustment is the problem. When adjusted by the book(clymer) screwed in until it touches and backed off quarter to half turn, the angle of the arm is approx 7 o’clock. The clutch action (from the clutch lever) is smooth. The clutch lifter slides in and out smoothly when the lever (handlebar) is operated.
I have just taken off the outer cover and the clutch lifter plate. The clutch plates all look correctly located within the basket. I will remove the clutch plates when I return from walking the dog. I have done this procedure at least half a dozen times over the past two years and it is doing my head in!

Any suggestions very welcome.

[Bryanj]

Dont know why but i think i read somewhere of somebody putting a washer in the wrong place. Take the whole clutch off and check with a parts book

[Nurse Julie]

I'm sure you have as you have been very thorough but have you got the clutch centre and the plate clutch lined up, ie, set in the correct position?

Photo 1, incorrect position. Photo 2 correct position (sorry, crap photo) . It needs to be in exactly the right position.

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[K2-K6]

Assuming that it checks out when you dismantle,  then try adjusting it as follows;- bring the adjustment screw in to touch and just make the smallest extra turn in the same direction (don't back it out) and assess it set like that.

This would be the most distance that the lift mech is capable of producing in giving space for the clutch plates to separate and would verify if that ability is there at all.

These clutch are unusual in that if the clutch pack heats up the thrust bearing moves away from the operating mech, with the likelihood of it slipping pretty remote.  But set like this will at least give an assessment as to if it's possible to get it to release the drive sufficiently.

Making the assumption that the handle bar clutch lever is a standard fitment?

[Bryanj]

Firther to my previous there is a splined waser that goes on the shaft before the pack of centre and plates, if that is missing, or in the wrong place the pack binds on the shaft

[Scottvincent]

Thank you for all responses. I believe that the plates are correctly located in the basket as they fit well down into the clutch basket. I will check again when I dismantle the clutch (too dark and cold at the moment!)
I have cross referenced the parts with an F1 parts book, all parts present and correct but, again I will check after dismantling.
If I give the adjustment screw an extra half turn clockwise, it slightly improves the situation but the bike is still not rideable.

I’m certain that I am missing something but cannot, for the life of me, think what it can be! I can see the bike being consigned back to the shed!

[Trigger]

Do you have a double steel plate in the stack ? And does the last plate in have slanted groves ? It would be helpful to see pictures of the assembly