Although BSA front forks are strong , well made and easy to service they are almost totally lacking in any form of damping , this can turn a pleasant ride into a wrestling match on bumpy roads . It certainly did on my first S-8 until I hit on the idea of fitting the internals from a pair of scrap Suzuki TS-185 forks . This worked very well and has been refined over several years to the system that I have used on three S/8s and one S/7 so far .
The original tapered bump stops are removed from inside the fork sliders and replaced by hollow damper rods and pistons as found in any modern forks . The lower fork bush retainers are modified to provide the seats for the damping valves whilst allowing a free flow of oil between the fork bushes , this prevents the seals being over- pressured by the fork action . The damping valves , which flow freely as the forks compress , then restrict the flow as the forks extend , are retained by inverted cups pressed into the stanchions.
Despite appearences this is not too complex a modification , although it does require quite a lot of parts to be made on a lathe ( 16 in total ) , the only really tricky part is altering the bottom of the fork sliders , you might have to farm this part out . The rest calls for a lathe and some skill in its use , a milling machine is also handy although these bits can be done by hand with care . The end result is a pair of forks that work as well as any I have ridden ever behind .
The set up is basically the same for S/7 and S/8 forks although the assembly is a little different due to the internal tapers of the S/7 stanchions .
Either set of forks requires 250ccs of Auto Transmission Fluid .
If any one is keen to try this let me know and I will send you the details .
EARLY SINGLE SPRING TYPE
I have never had the opportunity to study the early single spring forks , but it does seem to me that it should be possible to fit a normal pair of springs in the two fork legs and then replace the central spring-box with a short damper unit from an automobile . These come in a vast range of lengths and sizes so I feel that there must be a suitable one somewhere . If anyone tries this please let me know the result so that I can spread the word !!!!
