Classic Motorcycle Build

Norton Commando Build

After sitting in storage for 20+ years, this old neglected Commando will be needing a complete overhaul. The build will basically be stock, although during the reassembly process, I may decide on an upgrade or two.

Norton Commando build

1974 Norton Commando Roadster.

The first few months of ownership were spent going over the bike from front to back and top to bottom. Yet, there were still a few surprises once the disassembly began.

Is The Bike Worth It?

The Good Stuff - The frame is excellent, engine and frame numbers match, it has a clear title, and it came with boxes of good original parts.

1974 Norton Commando right side shift

It's also a low mileage bike, last registered 33 years ago. The speedometer and title show less than 10k miles.

The Bad Stuff - A major issue with this bike is the cylinder head.

stripped exhaust ports

Stripped exhaust threads.

The internal exhaust threads are stripped. This is not uncommon on Commando cylinder heads, as the screw-in exhaust nuts often vibrate loose and damage the port threads. But to make things worse, someone had previously tried and failed to repair them, and there are several broken and missing cooling fins.

850 Commando stripped exhaust ports

Repair or Replace Head?

I contacted Jim Comstock, a well-known Norton specialist. After looking at the pictures, he said that the fins and the exhaust threads were repairable, but he's back-logged with work for at least six months. I emailed several other places, but unfortunately, they don't have the same expertise as Jim does.

Plan "B" was to find a good replacement head. Either way, the old head had to be taken off.

Norton Commando cylinder head removal

Read: Norton Commando Cylinder Head Removal


After several weeks of sending inquiries to ebay sellers and classic bike specialists, I found a good used head on ebay.

Commando RH4 cylinder head

Truthfully, I paid more for it than I wanted to, but upon disassembly, found that the valve guides and seats were in very good condition. All the head needed was a good cleaning.

motorcycle cylinder head before cleaning

Decarbonizing The Cylinder Head

In the Norton Workshop Manual, there's a section on how combustion chambers and exhaust ports accumulate carbon deposits, and caution must be given not to scratch the aluminum alloy material while cleaning Do not use steel scrapers or a screwdriver blade!

"Old School" cylinder head cleaning with degreaser, brass cleaning brushes, a little Emery cloth, and a lot of scrubbing.

how to clean aluminum motorcycle cylinder head

Read: Clean Carbon Off Cylinder Head

It takes longer than vapor blasting, but it's cheaper and gets the same results.

Norton Commando replace cylinder head

The valves and cylinder head bolts were cleaned on a bench grinder with wire wheel attachment.


Why A Commando?

Why not a Bonneville, a BSA, or a another Harley Sportster?

For me, the answer is a mixture of reasons.

Of course, part of the Commando allure is it's looks. No-one can deny it's a fine looking machine, and here's proof--other than performance upgrades, most have been left original.

Unlike Bonnevilles and Sportsters, very few Commandos saw major customization. How many Norton choppers have you ever seen?

Another part of it's appeal is the company's historic racing history. During the 1930's, Norton accrued over 60 Isle Of Man TT wins!

Norton Motorcycle Isle Of Man TT

In the late 1960's and early 1970's, a Commando race bike wasn't that far removed from a road bike. Many will argue that Norton Commandos were responsible for the term "Super Bike".

Norton Commando proddy racer

Restoring a Norton Commando has a nice advantage over other classic motorcycles. Not only are all parts still available, they are nearly all still available as factory pieces, due in large part to the existence of Andover Norton. And there's plenty of modern upgrades as well.


repair broken cylinder fins on motorcycle

Before and after cracked fin repair, 850 Norton Commando.

repairing broken cooling fins

Read: Cracked Cooling Fin Repair


Up Next:

Top End Teardown and Inspection


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