B40 nut size

[PeteRae]

 
Hi folks,
Finally got around to stripping down my rather incontinent early B40 engine. Found a few problems, one being the use of metric bearings when it's been rebuilt in the past!! Doesn't help to keep things leakfree....
Anyway, Just about to split the casings and wondered if anyone knows the sizes of the casing nuts? There are two sizes and I don't want to start grinding down sockets to fit in the recesses until I know the size to use......anyone help please? Many thanks in anticipation...Pete....

[Mike40M]

What year is it? During their production years, BSA made a lot of changes on them. Could even affect nut sizes.

[DaveH]

Hi. My 1961 B40 crankcases use 3/16w size bolt heads & 1/4w size nuts. Equates to metric 11.3mm & 13.3mm so if you don't have any Whitworth/BSF  gear you might get 11 & 13mm to fit also 7/16af for the smaller ones. You shouldn't need to grind the sockets down to fit.

Cheers,   Dave

[AdrianS]

Invest in some imperial and Whitworth spanners and sockets. They are not that expensive and save a lot of hassle and rounding off of nuts. As said before, most of the fittings will be Whitworth sizes on the heads with a few AF ones as well. Thats what I found on my early B40.

[PeteRae]

Thanks guys,
The bike is a bit of a mongrel so nothing seems to match..haha....the engine number is B40 1973 which I reckon is an early Star...it's got sidepoints but retains the dizzy drive.
There doesn't seem to be much room around a couple of the recessed nuts in the cases but I'll get meself some whit sockets...only got AF and metric at the mo.
Cheers, Pete

[JulianS]

Consider 3/8 inch drive whitworth sockets - they are slimmer and fit places where a 1/2 inch drive will not and are very useful when working on a bike.

[PeteRae]

  Thank you for that.