Up for purchase is a great set-up for the Norton 920cc Commando with 81 mm pistons. This is an exceptional kit from JS Motosports that consists of what they consider: "The best piston/rod combination on the market. Our lightweight pistons (1/3 lighter than stock) are forged aluminum, making them stronger than original cast aluminum pistons. The combination of lighter pistons with our longer lightweight rods makes for a much smoother and reliable ride whether you are cruising down the highway or pushing it to redline on the racetrack. DYNO TESTS SHOW APPROX 7 MORE HP just by switching to the lightweight pistons and longer rods." We agree.
However, on my Norton Commando 920 build, the engine is already rebuilt and as such we did not want to take it apart again. In addition we are working on a Norton 1000 cc Commando that we are building from the crank up. My loss is your gain. If you have any questions, I would read the great material on the JS Motosports website.