Author Topic: Simplified diagram of BSA clutch  (Read 373 times)

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RogerSB

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Simplified diagram of BSA clutch
« on: 23 August, 2017, 17:01:10 »
My BSA GF has a 6-spring clutch, although working well, it doesn't have the adjustment I'd really like (and no I don't want to change it for a 4-spring version or a modification).  Laying in bed at 3 am this morning and thinking about it (like you do) I was trying to get my head around what, if anything, to do about it now. There are two things I suspect - but I won't bore you with that. I intend to strip it, fit a different cable and lever set up and renew the push rod when I lay the bike up after the summer but as I ride regularly I don't want to lay it up now unless I really have to - even for just a  day or so.

As an aside, I have been preparing for it and ordered a different cable, cable adjusters and a new push rod in preparation. The push rod was delivered from a retailer (with an f in their name) but it was undersized. They told me they couldn't replace it as all the push rods they had in stock were undersized (and they still advertise them) so I had to send the useless push rod back to them so they could have more of them (at my expense for postage I may add). That was a week ago and still no refund!!!

Anyway, I started to produce a very simplified diagram to show the relationship between the clutch adjusting components so I could study it without it just being a picture in my head and I thought it may be of use to some others to see a simplified diagram of what does what and how and so I added a bit of extra info for that reason.

« Last Edit: 23 August, 2017, 17:06:28 by RogerSB »
BSA Golden Flash, Plymouth, UK

TTJOHN

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Re: Simplified diagram of BSA clutch
« Reply #1 on: 24 August, 2017, 11:39:14 »
This is no different to what you already have, so I cannot see your point in this.

TTJohn

RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #2 on: 24 August, 2017, 17:03:08 »
It's a bit of a lengthy story to repeat here. That's in my previous post: 'Clutch cable ferrule and gearbox abutment puzzle' 9-8-17.

My A10 GF was delivered to a dealer in Bristol 7 Jan 1960 so it would have been assembled in the factory during 1959).

I recently fitted a new clutch cable pt no 42-8774 (for 1960 - 62 models). Gearbox inner cover has cable abutment lug for earlier 1958 - 59 models (with slot at top and internal thread for adjuster) so I had to modify the later cable's ferrule.

I'm thinking: Could BSA have assembled it with an earlier gearbox to use up previous 58 - 59 model parts. Or has someone in the past fitted the earlier gearbox. I know the internals are the same, only the control cables with adjusters at the handlebar levers and the cable lug on the gearbox was changed for 1960 -62.

What I was trying to fathom out is why I have 'only just' the minimum free play with the new cable and the drawing was done purely for me to have something to look at to help me to work out if anything else could be causing it.  I posted the drawing as I thought it could help someone else not too familiar with the working of the clutch.

I now think my lack of free play can only be caused by the combination of the later 42-8774 cable and the clutch push rod being too short, so my next step is to try an earlier 67-8681 cable with the adjuster at the gearbox end and fit slide-in adjusters at the handlebar lever end and if that doesn't solve it try a new push rod . . . . if I can find anyone who has one of the correct length.
« Last Edit: 24 August, 2017, 17:10:53 by RogerSB »
BSA Golden Flash, Plymouth, UK

Martin

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Re: Simplified diagram of BSA clutch
« Reply #3 on: 26 August, 2017, 11:20:43 »
Roger,

To a non-mechanical mind like mine, your diagram mirrors several sketches I made when I tried to fathom out the moving parts on my A65 Lightning 3-spring clutch, so you're not alone in resorting to the basics.

The clutch operation is really good now, even without the SRM modification, by tensioning the nuts so that only a light touch is needed on the handlebar lever, and after several exasperating attempts to get the plates to run in parallel I finally got them spot-on. I think that dealing with those two factors alone contributes more to the elimination of noisy clutches than anything else, in addition to the splendid advice I've had from experienced members.

bikerbob

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Re: Simplified diagram of BSA clutch
« Reply #4 on: 26 August, 2017, 15:01:32 »
As regards push rod length I believe the six spring clutch is 11.5" and the 4 spring is 12". If you have rod that is too short you could cut it in half and put a 1/4" ball bearing in the middle but you would have to harden the ends, some people do this mod anyway saying it improves the clutch operation, I did it on an A10 some twenty years ago but never noticed any difference in the clutch operationbut it was still working OK when I sold it 4 years ago.

RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #5 on: 27 August, 2017, 16:03:25 »
Thanks bikerbob,

I've been trying to buy one 11.1/2" long.  First one (pt no 42-3108) bought from f---- two weeks ago measured 11.3/8". I was asked to send it back for a refund because all they have in stock are undersized, so sent it back next day 1st Class - 2 weeks later still waiting for the refund. Second one from another online retailer measured 11.7/16.  >:(

No wonder there are so many problems with clutch.
BSA Golden Flash, Plymouth, UK

JulianS

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Re: Simplified diagram of BSA clutch
« Reply #6 on: 27 August, 2017, 16:14:44 »
The below parts service bulletin from 1956 shows the correct length for the push rod 42 3108 as 11 17 /32 inch.

I do not know why the 1954/55 push rod for swinging arm models was shorter at 11 13/32 inch?

RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #7 on: 28 August, 2017, 19:51:17 »
Thanks Julian, I did know the size should be 11.17/32". The only retailer I've seen that states that in their advert is Dragonfly. As far as I can tell most seem to advertise 42-3108 as 11.5". But it seems it's pot luck on what you actually get. I've tried two so far and both have been the wrong size. On the first one ordered I believed the advert and just ordered it, second one I made a point of checking with the retailer first and they confirmed the size but what I was sent was 11.13/32.  >:(  Thats 29-3860 for up to 1955.  So my next try is to order from Dragonfly to see if theirs is the length they actually state.

I think they just take us for a ride (excuse the pun).
« Last Edit: 28 August, 2017, 19:54:12 by RogerSB »
BSA Golden Flash, Plymouth, UK

JulianS

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Re: Simplified diagram of BSA clutch
« Reply #8 on: 28 August, 2017, 19:59:39 »
Have you tried C and D Autos?

Bess

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Re: Simplified diagram of BSA clutch
« Reply #9 on: 28 August, 2017, 20:16:38 »
Hi,
    Have you considered purchasing silver steel of the correct diameter, cut to length and harden the ends yourself. It saves all the heartache of suppliers providing the wrong item...

Best wishes....

RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #10 on: 28 August, 2017, 20:23:29 »
Hi Julian, no, not yet, must wait for a reply from from Dragonfly to confirm the size of the 42-3108 they advertise. If no joy I will definitely ring C& D autos (their website not up and running yet). Used them years ago for my D1 and C15 rebuilds when they advertised with whole pages of spares in Exchange & Mart.
BSA Golden Flash, Plymouth, UK

Bess

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RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #12 on: 28 August, 2017, 20:34:18 »
Hi Bess, thanks for reply. Yes and no, just wanted to save myself some work but may end up having to do that in the end.
First undersized push rod from f---d delivered just over 2 weeks ago, sent them an email same day as it was received pointing it out and reply received next day asking me to send it back for a refund because when they checked all their 42-3108 push rods were the wrong size. Fair enough, mistakes happen. Sent it back the next day by 1st Class post, but still no refund to date and no replies to my further emails.  :-\  They are still advertising it though!
BSA Golden Flash, Plymouth, UK

RogerSB

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Re: Simplified diagram of BSA clutch
« Reply #13 on: 28 August, 2017, 20:37:27 »
Thanks Bess, I'll make a note of it in case. I was going to ask you that in my reply a minute ago as I'm getting to the stage when I think if you mention Brit bike you'll be palmed off with something (like the wrong steel) and it'll be US.
BSA Golden Flash, Plymouth, UK

JulianS

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Re: Simplified diagram of BSA clutch
« Reply #14 on: 28 August, 2017, 21:06:28 »
A lot of poor quality parts around and unfortunately a lot of it comes from the same wholesaler and most sellers sell stuff from the same source so little real choice.

I like C and D because you get to talk to a real person rather than point and click. Same family since they opened in 1946.