The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Mosin on 16.12. 2018 11:19

Title: Primary chaincase screw sizes
Post by: Mosin on 16.12. 2018 11:19
Quick question: I am aware that two different diameters of machine screw are used to hold the primary case to the inner. The majority are smaller diameter of various lengths, but there are also three larger ones towards the front of the bike which go right through the primary inner and screw into the actual crankcase itself. Does anyone happen to know the size/dimensions of these three larger screws?

Thanks
Title: Re: Primary chaincase screw sizes
Post by: muskrat on 16.12. 2018 19:03
G'day Mosin.
42-7517 is 5/16 x 1-15/16 whitworth but I'd double check the length as if too long it will foul the crankshaft web.
Cheers
Title: Re: Primary chaincase screw sizes
Post by: Mosin on 17.12. 2018 17:53
Just the information I Was needing. Many thanks!
Title: Re: Primary chaincase screw sizes
Post by: Colsbeeza on 17.12. 2018 23:19
Hello Mosin,
Roger SB did a great job on this some time ago.

Check out  -  https://www.a7a10.net/forum/index.php?topic=13099.45

I have attached Rogers sketch, which shows lengths. I went through this a few months ago, and found Rogers sketch was spot-on.
Cheers
Colin
Title: Re: Primary chaincase screw sizes
Post by: a on 18.12. 2018 00:38
https://mikesclassiccyclespares.com/product/42-7517/
These are genuine BSA NOS ones if you'd like??