BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: BeenyBoy on 28 September, 2017, 16:52:32

Title: B31 Small end bush
Post by: BeenyBoy on 28 September, 2017, 16:52:32
Hi
Rebuilding a 1954 B31 and the small end bush is u/s- virtually in two pieces..so clearly a replacement is required. (Bike hasnt run since 1974 )
Obtained a new one but it is far roo large both internal and external. Now I've just had an interesting chat with a nice man at Hawkshaws who have stocks of "old" "new" stock but he thinks these were supplied "unfinished" by BSA and need to be machined (reamed) prior to fitting....anybody come across this situation ?

cheers
Title: Re: B31 Small end bush
Post by: JulianS on 28 September, 2017, 17:37:34
Small end bush is a press fit in the rod eye and will need very careful reaming or honing to suit the gudgeon pin.

The outside diameter should not need finishing before fitting.

Use a good quality sharp expanding reamer and take a small amount of metal with each cut, trying the pin each time.

The old Alpha bearings catalogues list small end bush dimensions, the B31 B33 bush is SE13 on the list with dimensions in the photo.
Title: Re: B31 Small end bush
Post by: BeenyBoy on 28 September, 2017, 19:35:00
Thanks for that... suprosed there not available "off the shelf" though

cheers
Title: Re: B31 Small end bush
Post by: Greybeard on 28 September, 2017, 21:23:57
I got my last one for my B31 from Draganfly because I was ordering a batch of Ariel stuff at the same time. It pressed in without a hitch - you'll need to make up or borrow a tool for getting the old one out and hhe new one in.
Wherever you get one from it will need reaming once its pressed in as its the only way of ensuring a proper fit. The pin is 3/4 inch but a 3/4 reamer will leave it as too tight a fit. An adjustable reamer is the easiest way to go as JulianS says. Just make very small adjustments until the pin is a nice sliding fit. Remember always to turn the reamer in the cutting direction only, never reverse it as thats a sure way of taking the edges off it
Dont use any kind of abrasive to ease the fit as particles will get trapped in the surface of the bush and accelerate wear.

Steve