Hi Paul I have just found your site and would like to see if some one can identify this piston It is 3and 5/16 ths inc in did and 31/2 inch in lengthIt has 3 comp rings all 1/8 thick and 1 oil ring also 1/8th thickslanted slots on the gudgeon sides IT IS STAMPED std ON THE CROWNIt is in a box marked Norton Villiers and it fits very snugly into the box and gives me the idea that it came fro Noton Villiers/ I have a 1963 ACL piston book and have been thru all tyhe engine sizes around this size but can find nothing with 4 rings all 1/8th each but no doubt some on will know it Regards Joe Brown Joe Brown

Solved: BSA motorcycle piston