| Listed in parts books | Not catalogued by year yet |
PISTONS BSA A10 8.5:1 040
An 8.5:1 compression, .040 oversize piston for the BSA A10 twin.
This is a piston for the BSA A10 twin, listed at 8.5:1 compression and a .040 oversize. The manufacturer code on file points to Amal, but that's a mismatch worth flagging up front - Amal makes carburetors, not pistons, so take that tag with a grain of salt and don't assume it tells you who actually cast this piston.
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We don't have much more on this one in our records beyond the compression ratio and the oversize bore. If you're rebuilding an A10 top end and need to match bore size, ring the shop with your cylinder's actual measured bore so we can confirm this .040 piston is the right one before it ships.
This is a BSA part, not a Triumph part, so don't cross-shop it against anything in the unit or pre-unit Triumph twin lines.
Sorry if we got something wrong here. If you think this information isn't correct, .