Please help identify fork legs for BSA B31 1958

[Flyn]

Hi all thanks for allowing me to join.
I'm trying to help my Dad as he's not very good with internet things like forums.
Please can you help identify these fork legs my dad has acquired for his 1958 BSA B31.
I'm servicing his forks for him & have bought new seals, stanchons & bushes for his year bike as his original parts needed replacing.

When servicing his forks we had to take his original forks to a local classic bike shop as we couldn't remove the old fork seals, but they squashed the thread section of the lowers so we couldn't use them again. So we have these new ones but my Dad didn't notice they're slightly different to his old ones, they have a hole inside the axel clamp into the fork internal. They also have no internal dampening rod thing like the old ones did.

We've checked the models over the years & we can't tell which year they're for & weather they're compatible with his bike. They have the holes in the bottoms like the "69-"70 but look like the older ones.

Any help would be fantastic!

[Flyn]

Hole sizes for bolt head & thread.

[Rex]

Can't help with a positive ID on that, but how dumb would any "classic bike" shop be to crush the legs beyond further use? Were they so far gone that you couldn't ease them back into circular?

[Flyn]

Can't help with a positive ID on that, but how dumb would any "classic bike" shop be to crush the legs beyond further use? Were they so far gone that you couldn't ease them back into circular?

Yeah I know right! I couldn't believe it! They were too far gone, I tried but you'd never get them back, we were so annoyed. Even more so that I had to force the old internals out with a brute force, trashing the old bushings. If I'd had known that they would've fouled up the job so bad I would have taken my dremel with a grinding bit to the old fork seals & save a load of trouble! Oh well live & learn I guess.

[chaterlea25]

Hi,
Classic bike shop ?
It never ceases to amaze me the butchery people get up to

To strip and assembly your forks you need a tool like this,
http://www.ebay.co.uk/itm/61-3005-BSA-FORK-SEAL-HOLDER-TOOL-A7-A10-A50-A65-B31-B32-B33-B34-B40-B44-M20-M21-/201854605772?hash=item2eff78d9cc:g:ZB4AAOSw9mFWI7PE

Find the BSA fork service sheets online for instructions,
I have found a problem with recently supplied fork bushes in that they are chamfered on the top outer edge
This means the bushes are not clamped tight when the circlips are fitted
A way around this is to machine the top of the bush and fit a suitable thickness shim to restore the fit
If the bushes are left with movement then you get an annoying hammering as the forks work
Shim packets are available from the suppliers of the fork bushes etc

The replacement fork leg you got is from a unit bike from the 60's, they had a rod damper setup
You need to get a matching leg and the rod dampers to get these to work
or an original 58 leg

HTH
John

[Flyn]

Hi,
Classic bike shop ?
It never ceases to amaze me the butchery people get up to

To strip and assembly your forks you need a tool like this,
http://www.ebay.co.uk/itm/61-3005-BSA-FORK-SEAL-HOLDER-TOOL-A7-A10-A50-A65-B31-B32-B33-B34-B40-B44-M20-M21-/201854605772?hash=item2eff78d9cc:g:ZB4AAOSw9mFWI7PE

Find the BSA fork service sheets online for instructions,
I have found a problem with recently supplied fork bushes in that they are chamfered on the top outer edge
This means the bushes are not clamped tight when the circlips are fitted
A way around this is to machine the top of the bush and fit a suitable thickness shim to restore the fit
If the bushes are left with movement then you get an annoying hammering as the forks work
Shim packets are available from the suppliers of the fork bushes etc

The replacement fork leg you got is from a unit bike from the 60's, they had a rod damper setup
You need to get a matching leg and the rod dampers to get these to work
or an original 58 leg

HTH
John

Hi John, thanks so much for the reply, not impressed with the "shop" at all!
Have one of those tools & used it, but the fork seals were seized so tight the teeth on the tool rounded off!!

We also have relevant manuals so instructions are all good too.

Thanks for the advice on the bushings, I'll check our ones, & thanks for clearing that up for us regarding the new legs, it was what I suspected , but needed confirmation. As we've got brand new stanchions etc we'll go back to the exchange our '60's lowers for compatible earlier lowers.   

[iansoady]

It's worth remembering that BSA fork stanchions* are multiple diameter for some unknown (to me anyway) reason so you can't just slide the seals down over the top as you would with a Norton etc. The diameter that goes through the bottom yoke is bigger than the bearing surface - but only slightly so the seal will actually go over it but be wrecked in the process.

So you have to drop all the stuff off the bottom, fit the seal from the bottom end then keep it in place while you wangle that horrible circlip back into position.


*at least they were on my similar vintage A10

[Flyn]

It's worth remembering that BSA fork stanchions* are multiple diameter for some unknown (to me anyway) reason so you can't just slide the seals down over the top as you would with a Norton etc. The diameter that goes through the bottom yoke is bigger than the bearing surface - but only slightly so the seal will actually go over it but be wrecked in the process.

So you have to drop all the stuff off the bottom, fit the seal from the bottom end then keep it in place while you wangle that horrible circlip back into position.


*at least they were on my similar vintage A10

Great tip! I'll be sure to keep that in mind, thank you so much!