Norton Commando Rebuild 2011, By Dale Knaus

As most of you know, my pride and joy is a pretty stock 1975 Norton Commando Roadster that I purchased from past member Bill Henderson in 2001.  It’s been a very enjoyable and reliable motorcycle, (except for that little problem with the transmission layshaft bearing several years ago.)

Well, the Mark III had been getting a little tired lately, it seemed down on power and running a little rough, and not starting on the first kick like it used to.  I regularly take it to Columbia Missouri, a 200 mile round trip, and in that mileage it goes from the full mark on the oil dipstick to the add mark, about ½ quart.  Some of it is leaking, some burning.  I had been thinking of tearing it down for a rebuild, but being currently between jobs I figured sure as soon as I got it spread all over the garage someone would want to employ me, probably out of state, and I’d be moving the proverbial basket case.

Well, on July 9, I took the 850 up the river road to Hannibal, and rode around a while.  Coming home, the odometer hit 35,000 miles.  Cool, me thinks.  Just 17 miles later, the speedometer drive gearbox on the rear axle puked it’s guts out, and the speedo quit working.  Hmmmm. A bad omen, maybe?

I gassed up in New London, and hit highway 61 to come home.  I decided to get on it for a change, usually I don’t ride the bike very hard, and I discovered it ran out of steam at about 5,000 RPM!  She would hardly climb above that limit in any gear.  During a long, long distance phone call to King Mike French, I learned the low power was one symptom of a flat cam.  Hmmmm.  A lot of research on the subject, and it seems a lot of Mk III cams were flat at 12,000 miles.  My bike had more that twice that mileage. Hmmmm again.  Well, putting it all together, it seemed like a good time to consider the rebuild.  

As luck would have it, the following Friday I got a rejection notice from the Kansas based company I had interviewed with, and Saturday I started teardown on the old Norton.

That little remnant of a cam lobe is still the original cam profile, giving some idea of how much was worn off.  The cam tappets were pretty worn too, as you can imagine.

Surprisingly, the bike had not been bored.  In fact, other than the cam and tappets, and the rings on the right cylinder worn out, it was in pretty good shape!  It showed no signs of ever having been apart before.  

I’m going to reassemble with a new cam and followers, and new piston rings.  It also needed new intake valve seals and we put new exhaust valves in. The cylinders got honed and the original pistons are cleaned up for reuse.

After staring at all the parts, I decided to paint the engine before reassembly, and that’s the phase I’m in now.  Next month I hope to report on progress, if there is any.  By the way, I got a job offer (and accepted) the day after I split the cases, so work is progressing slowly.

Copyright -Dale Knaus 2011, used with permission by the EMU