Swap out the front end of an old BSA A65

Psychopasta

Been Around the Block
Hi,

I'm restoring an old BSA A65 which has had its front end replaced with a Betor front end. The problem is, this is quite long, and it was put on from the days the bike was raced. It has no mounting points for mudguards, or anything really.

So, I'm thinking of putting the front end from another bike onto it. First of all, are there any good threads on here about doing this specifically? I know lots of people do this as part of their own restorations, but I've not found anything describing the process in general.

I don't want to modify the frame of the BSA, so I guess the only thing that transfers from the old bike is the headstock length and angle. What process do I go through to identify and then source a replacement front end?

- Mark
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
Two things to think about. First is can it fit? and that comes down to steering stem length and diameter and what bearings are available to make it work. If all else fails, the steering stem can always be cut off and lengthened or replaced. That's just work.

Second thing is geometry. measure teh length of the forks that are fitted and if possible get a BSA owener to measure a set of OEM forks. Then measure the offset (center line of the fork tubes ahead of the center line of the steering stem/headstock. try to find a set of forks that are dimensionally similar. Shorter than stock lowers the front end decreases rake angle and gives less trail and less stability.

Less offset than stock (modern forks) gives more trail and more stability.

After you work all that out, obviously you want stiffer than OEM forks and some with better damping if at all possible , but start with basic dimensions.

As to how to find a set of forks with similar dimensions, ask around for people with say T120 forks to measure them or GT750 or GS1100 forks or whatever takes your fancy. Or just buy a few different sets until you find what you want but that could be an expensive hobby.

If you measure your forks and post the dimensions, maybe the rest of us can measure what we have and build a database of sorts. What diameter are the Betor forks that are on it? If they are 35mm, they are probably better than most forks from the era.

You might lso be able to bore out the triple clamps to fit slightly larger fork assemblies without swapping the triples.
 

johnu

Over 1,000 Posts
DTT BOTM WINNER
Would it not be easier to look for original A65 forks. I don't think they are especially hard to come by.
 

ex119x

Been Around the Block
I think the easiest would be to find a more modern fork with the same diameter tubes as the Betors and either just slide the forks into the Betor triples or just use the newer sliders on the Betor tubes. Either way, you will have to figure out spacers for the front wheel and get the brake alignment figured out.
 

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