Hi,
Bought a set of A7 cast iron barrels complete with pistons but?.the pistons are very different. Trying to work out the bore size assuming these pistons were run in these barrels?
In the photos below:
The left piston has the BSA part number 67-1445 and ½ N/M OS plus some smaller figures too indistinct to make out. Weight 9 grams.
The right piston has the number 11603 and something like 0.2 (?), plus ?Made in England? ? it also has a larger cutaway beneath the oil scrapper ring. Weight 8 grams.
I would expect to see +30 or the likes of ? not come across these markings before; am I correct in assuming they are both +20?
With the weights being different presumably they shouldn?t be used together?
Does the larger cut away beneath oil ring improve performance being lighter and oil flow or some other reason?
What does the N/M stand for??
Any info would be appreciated to improve my little knowledge
Cheers
Road Runner