The Story of a Norton Commando Racing Motorcycle Rebuild

Part 4

January 2003


To build a nice racing motor, it is important to balance the crankshaft, pistons and connecting rods.


The Commando has a 3-piece crankshaft, although solid cranks are available from Nourish racing in the UK, at great expense and considerable increase in weight. Les Emery at the great Norvil Motorcycle Company says that 3-piece cranks are OK for 750 Commandos, but the one-piece cranks are best for 850 and 920 engines.

Here, the crank is in pieces, being cleaned out, in preparation for balancing.

After having the crank, new connecting rods, and new pistons balanced, it all must be assembled. It is a good idea to use new crankshaft studs and nuts to rebuild the crank.

I decided to have Rick at Rabers in San Jose, California, do the valve job on the head. One valve guide was damaged due to the valve hitting the piston. We replaced the valve guides, seated larger Black Diamond valves, installed and packed racing valve springs to match the lift of the new camshaft that I chose.


I went with a 5600 Megacycle racing camshaft, from Santa Rosa, California. Megacycle makes great cams, with an excellent reputation for reliability. Even the Norvil folks recommend them. After witnessing the disintegrating Dunstall cam, I was quite eager to try the Megacycle cam. Interestingly the threads in the camshaft that drive the timing are metric in the Megacycle cam, whereas they are Standard thread in the original Dunstall cam. Here's my 4 year old son Aiden posing with the cam.


Click here for chapter5 and the saga of the camshaft.