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Thread Like Summary
BSA_WM20, Gary Caines, Gordon Gray, kommando
Total Likes: 10
Original Post (Thread Starter)
by Gary Caines
Gary Caines
When I try to start my 1969 BSA 441 Victor Special with the kick starter, the clutch sometimes slips. I found a video on You Tube showing a similar problem with a 1968 Starfire.
In that video, the BSA mechanic removed the primary cover and tightened each of the 4 spring screws one full turn to correct the problem. I have no idea if this is a legitimate way to cure this problem or not. Does this sound legitimate and if so, is one full turn per screw reasonable?
Liked Replies
by kommando
1 member likes this
by gunner
This question crops up all the time especially with BSA unit singles, I agree with what Gordon and others have written above and my thoughts are as follows:-
- make sure you have the right springs and cups fitted, its common to find mismatched parts so check and measure everything.
- screwing in the adjusters to stop slip is a playoff between easy or hard handlebar action, personally, I go for screwing them in all the way and then out enough to allow full disengagement with the handlebar lever pulled in.
- check that the right oil is being used, it should be a motorcycle wet clutch compatible (JASO MA spec), a classic car oil no higher than API SF/SG or auto trans oil type F, you might need to clean the plates with solvent if the wrong oil has been used.
- the adjusters should be lock-wired as they tend to loosen easily.
- consider doing the 6 plate conversion as specified on the BSA B50 website Here
- use surflex clutch plates which are grippier than the originals.

The B44 clutch can be made slip-free with a bit of time and effort if you keep at it.
1 member likes this
by Gordon Gray
Gordon Gray
I should know better but I’ll give it a try. This is opening a can of worms.

To answer your question one turn in is okay IMO but…..

Does the clutch slip? High gear going up hill?

If it does then you might need to tighten the springs. Some say the spring end should be flush with the spring cup. Some say one coil above. There was a change in the spring and cup. Some springs and cups are shorter than others. Springs lose tension so measuring free length is important. Also over tightening the springs can cause coil bind and a heavy clutch lever pull. So you could have some adjustment left or the springs could need replacing.

Then there’s the pressure plate run out which is adjusted by the spring pressure.

I’ll not go into the different ways BSA tried to keep the springs from backing off…..easier to use what you have

If it’s not slipping when you’re riding it……….stop trying to kick it through compression.

Getting to it is easy and should be something you do for regular maintenance.

But do your homework first. Then pull it apart and have a look.

Good luck, Gordon
1 member likes this
by NickL
If the 10-30 motor oil used was a modern type, you've stuffed the plates.
Once you have friction modified oil on the fibre plates they are for the bin.
1 member likes this
by kommando
I have a fully functioning decompressor but never use it, rest the foot on the kicker when it hits compression and let it slowly leak away. Must put the decompressor lever in a better place one day.
1 member likes this
by Mr Mike
Mr Mike
In my opinion, the clutch for unit singles was probably under designed for all but the early 250ties. The 67/68 Starfire 250 with it's high compression and the B44's took the clutch beyond it's limits or at best right to their limits. I converted my B44 to add an extra plate per Rupert Ratio using Surflex plates. A very worthwhile improvement. For my B50 I made it a six plate clutch and it has the lightest pull clutch of any of the unit singles I have owned and it does not slip at all. I have a writeup on this modification somewhere if there is any interest.
A point made by others. Don't start under only wears things out. I don't get on this great site much anymore as my riding days are dwindling and I am down to a single BSA.... a B50. i sold my last B44 (somewhat regretfully). That bike is what motorcycles are all about. I am not into these new fangled bikes that that rev near five digits and have more HP than the cars I grew up with.

Hey there Gordon!

Mr Mike
1 member likes this
by Mr Mike
Mr Mike
I never experienced (that I know of) the nuts backing off but had all the other problems. I once tried those heavy duty springs to prevent slipping but that made for hard lever pull. The extra plates (Rupert ratio idea) and my six plate were the best improvements I have made. Your also have to get all those little things right too. I have seen actuating arms that do not pass thru TDC, short push rods, sticking plates as well as slip. I really like Rickards idea of welding the last plate to the pressure plate.

Great fall weather we are having!

Mr Mike
1 member likes this
by Mr Mike
Mr Mike
Gordon, I don't know why some people don't share their successes. Your side car rig could probably benefit from the six plate clutch ((22% more surface area.).

I got a few calls from the guy that bought my A65 that I sold to Richard. He quizzed be about the modified oil pressure system I had installed. He says It still has fantastic oil pressure and it runs good. I was glad to see some one else getting to enjoy an old resurrected BSA. That oil pressure system was one of my better ideas that really worked.

I do a lot of sailing now. They are easier to fix up and rarely break down, but like bikes I now have too many of them.

Mr Mike
1 member likes this
by Mike Baker
Mike Baker
I have come to accept that a clutch will last 2 maybe 3 race weekends in my B50. I've tried Barnett, Sureflex and Emgo plates, all the same. Just put a set of new Emgo's in for Barber- Gumby is riding it. No sense paying $100 for a clutch when a $50 clutch does the same thing.
Re: Mr Mike's mod, I got everything in there but it looked like there was 10 lbs of sh*t in a 5 lb bag. I may need to revisit it this winter.
1 member likes this
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