Norton Commando Roadster Idling Problem

Reader Contribution by Keith Fellenstein
Published on September 21, 2016
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Norton Commando idling problem

Q: About two years ago I bought a 1974 Norton Commando Roadster that was  in excellent original condition, with one exception: The left cylinder doesn’t fire regularly at idle. I had the original ignition upgraded to a Pazon electronic ignition, but the problem remained. I replaced the original Amals with new ethanol-resistant Amal carburetors, and still there was no improvement. I also tried reversing the coil wires to see if the problem changed sides, and the left cylinder remained anemic at idle. I recently replaced both coils, plug wires and plugs, but the problem remains. The old plugs indicate rich running on the left, which I think may be due to no fire at idle. The bike runs great otherwise, and is a joy to ride. I’ve compensated by using the idle mixture set screws to maintain a slightly higher idle, but the right cylinder is carrying the load at idle. Do you have any ideas why this is happening after installing new Amals and the Pazon ignition? Emmett Fox/via email

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