BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: DEDGE on 04 May, 2018, 19:05

Title: B31 clutch
Post by: DEDGE on 04 May, 2018, 19:05
Hi Guys
More help with my 1950 B31 plunger rebuild please. The clutch was a mess of bits when I got it so dummy run putting it back and lining it up.
Picture shows the clutch sleeve goes up to drive sprocket net, book says should be felt and cork washer there ( sleeve oil ring collar not on there yet).
Does anyone know the length of main shaft from sprocket nut to shaft end Picture 2
Have I got the wrong main shaft (the gearbox seemed right) or the wrong sleeve or just doing it all wrong
Picture 3 view of drive sprocket.
All The Best
Dedge

Title: Re: B31 clutch
Post by: GBonduel on 05 May, 2018, 07:36
You seem to be doing OK, I'm guessing you're using this diagram:

Don't have the exact measurements but I do remember it looks too short but once everything is assembled it works.
Title: Re: B31 clutch
Post by: DEDGE on 07 May, 2018, 21:12
Hi Guy's
Still trying to sort out my clutch, as to whether the main shaft is wrong or the clutch sleeve. Both look right by looking at parts book pictures. But the clutch sleeve slides on and of by hand  and not wedge on the tapper. The 1949 parts book list it as 66-3799 and the picture looks the same but dragonfly list it as
65-3873 and again the picture looks the same does anyone know if theses two part numbers are the same.

Dedge
Title: Re: B31 clutch
Post by: JulianS on 08 May, 2018, 10:20
The 1948 1949, 1950 and 1951-52 all model parts books all show the clutch sleeve as 66 3799, the mainshaft as 15 4260 and spring frame chaincase back as 65 7578.

The B series 1949-53 book shows the sleeve as 65 3873 with the mainshaft and chaincase back remaining the same part. So the sleeve does interchange. The mainshaft goes back to the 1930s.

The 1948 engine plates were different parts to the 1949 and later but I dont know what the differences were.
Title: Re: B31 clutch
Post by: Dan_B33 on 27 Nov, 2023, 14:28
Think I have same problem. What was the sillution?
Title: Re: B31 clutch
Post by: neil1964 on 30 Nov, 2023, 17:04
Quote from: Dan_B33 on 27 Nov, 2023, 14:28
Think I have same problem. What was the sillution?
You are not the first to have this issue.  The M20 and early box types and 51 plunger are all different afaik. I only have s/a boxes but suggest read this:

https://www.britbike.com/forums/ubbthreads.php/topics/871155/re-finding-the-right-clutch-package (https://www.britbike.com/forums/ubbthreads.php/topics/871155/re-finding-the-right-clutch-package)
I also suggest you read this:
https://www.britbike.com/forums/ubbthreads.php/topics/674773/bsa-6-spring-clutch#Post674773 (https://www.britbike.com/forums/ubbthreads.php/topics/674773/bsa-6-spring-clutch#Post674773)
Title: Re: B31 clutch
Post by: cdsdorset on 30 Nov, 2023, 21:05
Do you have the earier gearbox fitted. Where is the speedo drive mounted?
Title: Re: B31 clutch
Post by: Dan_B33 on 01 Dec, 2023, 11:25
Here is teh gearbox I think it is later version.
Title: Re: B31 clutch
Post by: Dan_B33 on 01 Dec, 2023, 11:27
Main Shaft is like that on picture
Title: Re: B31 clutch
Post by: Dan_B33 on 01 Dec, 2023, 11:31
And picture
Title: Re: B31 clutch
Post by: Dan_B33 on 01 Dec, 2023, 14:39
Clutch sleeve is in matching shape but the fit is not tight
Title: Re: B31 clutch
Post by: cdsdorset on 01 Dec, 2023, 20:00
You may have the earlier gearbox sleeve ( pretty rare now) virtually identical but the internal taper is a different angle.
Title: Re: B31 clutch
Post by: Dan_B33 on 02 Dec, 2023, 10:02
Thanks cdsdorset,
I'll compare with sleve I've brought on eBay. I hope they differ an that the one from eBay fits...