| Listed in parts books | Not catalogued by year yet |
PISTON BSA M20 +.020
A +.020 oversize piston for the BSA M20 single.
This is a piston for the BSA M20, machined to +.020 oversize. The M20 is a BSA model, not a Triumph, so if you're working on a Triumph twin this one won't apply to your build.
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The +.020 designation means this piston is sized for a cylinder bore that has been rebored .020 inch over standard, which is a common step when a worn bore gets cleaned up and the original piston is no longer usable. Ordering the correct oversize matters here since a piston sized wrong for the actual bore will bind or run loose no matter how good the rest of the rebuild is.
Our catalog record on this one is brief, so if you're not certain what bore size your M20 has been taken out to, give us a call before ordering and we can help confirm you're getting the right piston for the job.
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