While I've got my clutch in bits, I was just wondering: when I put my bike into gear to set off, it goes in with quite a clunk. Is that normal, or is there something I should be looking at? Phuil.
Phil not unusual for there to be a clunk when engaging first, it is the clutch plates not freeing. Before starting the engine try pushing the kickstart down a few times with clutch lever pulled in this usually frees things. Also worth checking the togues on the plates and the slots in the chainwheel and hub and dressing with file if necessary.
Okay, thanks Julian.
Whilst waiting for tools to arrive to continue my search for a leak, I thought that, as I've got the clutch in bits, I'd have a look at this (see photos attached). I think its called a cush drive unit and I'm guessing the rubbers inside act as shock absorbers when using the clutch? Anyway, to my inexperienced eye it looks as though it could do with new rubbers? I have some as shown which will hopefully fit. Is this in as bad a state as it looks to me, and what effect would it's condition have? Thanks again in advance.
Phil.
Could anyone reassure me that these are the correct rubbers please? I think they'll be a very tight fit - is that how they should be? Thanks. Phil.
The rubbers for the later clutch are like rubber buttons, same part used on B25 44 and 50;
https://www.ebay.co.uk/itm/BSA-UNIT-SINGLES-41-3212-SET-CLUTCH-CUSH-DRIVE-RUBBERS-C15-B40-B44-B50/252896775421?hash=item3ae1d28cfd:g:e
Can be difficult to fit you need to slightly compress one to fit the other - the later workshop manuals recommended using liquid soap as lubricant to assist.
Does anyone know which type I should use on my 1965 B40F?
Part 41 3212.
Below from 1965 parts book for B40F engined models.
Thanks Julian. That looks like a smartie-shaped one. The one I was sent under that number is the one on the photo (below). I'm wondering: does it matter ? Maybe either is okay?
Also, are they meant to be a very tight fit?
Phil.
Actually, I've just phoned the people I bought them from, and it turns out they got the part numbers mixed up and sent me the wrong ones. They're now going to send the correct ones, which they tell me are the smartie-shaped ones. Fair enough. Glad I know now anyway. The old ones look a bit worse for wear, don't they? Phil.
The smartie shaped ones, which I called button shaped are the right ones much easier to fit than the wedge shapes.
I would certainly replace the ones in the clutch - hope that there is not too much wear to the spider.
Talcum powder's a great help to get cush drive rubbers in place, and less messy than liquid soap.
The clunk going into first is nowt to do with clutch rubbers
When the gearbox is in neutral the clutch and mainshaft are spinning, the layshaft is stopped. When you pull the clutch in, the mainshaft is still spinning by inertia, clutch drag and bearing drag. Engaging the gear stops the shaft as the dogs engage, the clunk is the backlash in the dogs.
Even if the clutch is not dragging there will be drag between the plates due to movement of air and oil.
Suzuki GT380 triples had a clever little brake in the first gear pinion, when you pressed the lever a little arm contacted a plain portion of the gear stopping it from rotating thus stopping the clunk
Thanks everyone. Out of interest, what do the rubbers do? Phil.
They take the shock when you dump the clutch
How on earth do you get the rubbers in? I've got the black ones, shaped a bit like smarties but fatter. I've not tried talcum powder (as recommended by Mark B), because I haven't got any, but I've put on liquid soap (Tesco aloe vera and cucumber extracts, no less) and pushed as hard as I can (I'm fifteen stone and like to think have strong hands) and can't for the life of me get them in. Any advice please? For example, is it best to put them in two at a time, or drop one in and then try to get the other in? Phil.
Actually I think I've now found a knack, squashing the rubber sideways with the end of a metal strip whilst pushing down with the the thumb, using a little bit of the liquid soap as a lubricant. Not sure if it only works with the aloe vera and cucumber extracts. Phil.