AJS & Matchless Owners Club

Will a Hepolite piston ref no 10049 for a 1947 AJS /Matchless, fit a 1961 G3LS? Any advice appreciated, thanks Tony.

Try F W Thornton in Telford, worth a call or e- mail. Or Russell's motor's London they loads of old stock.

The 1947 piston has the lower gudgeon pin for the first year of the 6 7/8” connecting rod and a compression ration of 6.35, this was a one year only piston not sure why but the following years sales brochure makes reference to a “lo-ex” piston so this may have been the change. The engine had an iron head.

The 1961 engine uses the same connecting rod but the compression ratio was 7.5, and had an alloy head. So in theory the piston should fit but the compression and power would be down, you would need to check that the valve clear the piston (shouldn't be a problem) but you would do better to find the correct piston.