The Story of a Norton Commando Racing Motorcycle Rebuild
In 1972 Norton introduced the Combat engine, a Commando engine with raised 10.1 compression. These motors had increased power over the standard Commando engine, and were very popular. Unfortunately for those lucky Combat engine owners, the crankshaft bearings proved unable to handle the increased power of the engine, and promptly disintegrated after about 3,000 miles.
The solution was to replace the bearings with much more robust roller bearings for the crankshaft.
The subsequent warranty claims and remanufacturing of the engines on the Norton assembly line no doubt contributed to the eventual demise of the Norton Motor Company.
Here's the crankcase after I heated it up, popped out the old bearings, and inserted the new "Superblend" roller main bearings.
And here we are with the new connecting rods and bearing shells for the big ends of the rods.
We polished up the connecting rods before installing them, to remove any imperfections that could cause fractures and failures at high RPMs.
Click here for chapter 4 and the crankshaft follies.