BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: Martin on 11 May, 2017, 10:22:40

Title: Plunger, clutch operating lever on a 1968 A65 Lightning
Post by: Martin on 11 May, 2017, 10:22:40
I'm having trouble getting the clutch plates on my A65 Lightning to separate sufficiently, and should be glad of suggestions how to overcome this.

Part-cause might be the plunger, clutch operating lever (part 68-3065). Never having taken it out before, I don't know where the ball (part 65-2593) should sit, so I attach a photograph of the business end, from which it seems the ball might have worn so much that it has lodged deep inside instead of projecting further out like an egg in an egg-cup. My non-engineering thought is that, if the ball sat proud of the plunger's end, the effect might be to lengthen the push rod that little more so as to free the plates better but, against that, the pressure plate might then make contact with the chaincase. Where should the ball sit?

Though at its limit on the adjuster, the cable is in good condition and the slack is kept to a minimum. The push rod is 11" long and shows no sign of wear at either end, and the screw on the pressure plate has been adjusted to give the right amount of clearance between plate and push rod. The plates themselves have been cleaned in petrol (they were pretty grimy), they're perfectly flat and have no rough edges or anything else to impede movement; neither has the clutch housing - yet, with all this, I still get a horrid crunching noise whenever engaging first gear from neutral. All other gear changes while in motion are fine.

All helpful advice will be much appreciated as, apart from the plunger, I've run out of ideas!
Title: Re: Plunger, clutch operating lever on a 1968 A65 Lightning
Post by: JulianS on 11 May, 2017, 10:59:00
Some  thoughts:

The ball should be 7/32 inch diameter - you could measure the bore of the housing to check its the right one. New housing and balls  are cheap enough.

With the plates out does the hub rotate with minimal drag on the chainwheel - if not then could be a problem with the thrust washer causing the drag and hence crunching.

Does the pressure plate lift cleanly, if not adjust the spring screws until it does. SRM type alloy plates give more even and clean lift in my experience.

With a cable at limit of adjustment I would shorten length of inner  cable by moving one of the nipples to allow adjustment of length on cable adjuster.

Handlebar  levers originally came with pivot to nipple centres of either 7/8 inch or 1 1/16 inch. The former give lighter more progressive movement with less lift at the clutch and the later give heavier less progressive movement but with more lift at the clutch.

Title: Re: Plunger, clutch operating lever on a 1968 A65 Lightning
Post by: Martin on 11 May, 2017, 13:43:39
Thanks, Julian - you've given me a few other things to try. The ball doesn't want to come out easily, and that may be because it's worn and got stuck, but when it's out I'll measure it. The handlebar lever is 7/8", so the other type could do the job. Thanks again.
Title: Re: Plunger, clutch operating lever on a 1968 A65 Lightning
Post by: Bess on 11 May, 2017, 15:41:34
Have you seen this ?

Title: Re: Plunger, clutch operating lever on a 1968 A65 Lightning
Post by: Martin on 11 May, 2017, 20:24:23
Thanks, Bess and no, I hadn't seen that before.

All three clutch spring nuts are adjusted to round about the same degree shown in the illustration, and the plates are as near alignment as I can make them by line of sight.

I still don't know whether part of the ball should protrude from the end of the plunger but, if it should, then that's likely to be the cause of the crunching, as it's sitting well inside the recess and must therefore reduce the effectiveness of the pushrod on the pressure plate. As Julian says, new parts are comparatively inexpensive, so I'll replace what I've got.

Thanks again.