BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: fergusandted on 14 June, 2017, 20:58:39

Title: New to world of B31s
Post by: fergusandted on 14 June, 2017, 20:58:39
Hi I'm new to the club and forum over the years I've owned lots of big singles British and Japanese
But have just bought my first B31
It's a 1950 ridged it's pretty standard and has its original engine and frame
I have 2 problems if anyone can help
How do I fit the Magnito pinion accurately ? On my AJS I just put a socket against it and give it a sharp tap but that doesn't seem to work on the beesa it won't lock onto the tapper
Also the bike is running very rich it will only start with the throttle wide open and the plug is black with soot not oil its has a 376 mono block with the right size jets and cut away I've rebuilt the carb with new gaskets and float needle
The ignition timing is close considering pinion problem but I don't think that's it
I'm missing something just don't know what
Title: Re: New to world of B31s
Post by: JulianS on 15 June, 2017, 09:22:09
The pinion should tap onto the mag shaft just like your other bike so it suggests that the taper is worn or damaged.

As for the rich running  the carb could be wrongly assembled.

Check the joint between the float needle seating and carb body.

If the carb has a recess as the photo then it is a "new" type monobloc (which takes the thin cross section o ring) and there should be a fibre washer between body and seating.

If the body is flat no recess it is an old or original type monobloc (which takes the thick section o ring) and the joint should be metal to metal. Sometime a fibre washer is wrongly fitted in this joint. It raises the float level and can cause flooding and rich running.
Title: Re: New to world of B31s
Post by: fergusandted on 15 June, 2017, 10:02:12
Thanks for getting back so quick
I checked the Mag shaft and it looked fine the pinion had no thread for the puller so I replaced it with a new one (which may be the problem )
The mono block is a old type (thick O ring) and I've tried it with and without a fibre washer under the seat
I'll get back in the shed over the weekend and crack on again