3 replies to this topic

[bobtlr]

Hey

i have a Bsa B40 GD now but i would like my bike to be a bit more nervous and powerfull.
the bike has a standard piston for now but i would like to know if there if a piston available that gives higher compression (from a road version of the b40?)
and can i just change my piston ( it has a flat surface) for a high compression piston or do i have to balance the flywheel and do other stuff to my engine?

best regards bob

[piston197]

Basically there were 2 pistons used in the B40 standard ratio 7:1 and higher comp version 8.75:1,the higher one now seems to be favoured by the more experienced(and more aggressive riders),i still have about half a dozen of these all 1/2mm (+020) oversize,can deliver to the bonanza if anybody wants one,the low comp piston measures 1.608" from centre of pin to top,high comp piston measures 1.801" for identification. Pistons i have are all genuine BSA

[bobtlr]

can i just fit one of these or do i have to balance the engine after fitting this?

[piston197]

No,balance factor same for both pistons,if you need on phone me 01989 750731,John