Smaller piston which fits into a copper 3/8" coupling.

This is a modification to add durability to the engine as well as a better fit to the piston & cylinder. The original cylinder wasn't completely round, and was a larger size than the remixed cylinder. This cylinder could fit into a 3/8" copper coupling which is now a cylinder sleeve. The copper sleeve needs to have five 1/16" holes drilled to match the air holes in the cylinder. Drill these holes with the copper coupling in the cylinder head, then file down the inside of the coupling. I wasn't a