Ive recently replaced the seals, bushes and springs on the forks on my 1953 plunger frame B31.
The bushes supplied as being correct are longer than the ones fitted previously. The new ones are approximately 2 inches long whereas the old ones were more like 1 - 1 1/4 inch long. The new ones I have fitted match the part number according to Draganfly's spares diagram.
I have also fitted progressive fork springs which are around an inch longer than the old ones. I have assumed that the old springs have sagged as they are also different lengths to each other.
The culmination of this is the forks top out earlier as the increased preload makes the fork float with the lower bush closer to the now longer top bush. This results in a clonk as the forks top out going over uneven road.
I'm tempted to remove the bushes and shorten them. I think the originals were probably C15 size.
Can anyone let me know if this topping out is common on B31 forks and also what length top bushes you'd expect to have fitted.
Thanks.
Sounds like you were supplied the wrong bushes. The plunger B31/33 used a short top bush and different shafts and springs. Presuming the bike has the original type shafts it probably sits lower at the front wheel with the long top bushes and the progressive springs would be more compressed causing the topping out.
Have a look at the parts book and you will see what I mean.
Thanks. I must admit I find logging into the members bit a bit of a pain so tend to use the Draganfly spares diagrams ::). Sounds like shortening the bushes may be the way to go.
The original top fork bushes were longer but reduced the fork travel so BSA shortened them back in the early 50s.
Sorted - whipped them out and turn them down to the same length as the old ones. Clunk gone :)