74 Norton Commando Timming

I just put new pipes on the Commando and have not ran it for some time and it ran badly and blued the right pipe big time. It has a boyer on it and a mikuni. It was missing and back fireing. It ran better with the choke on but when the choke was off it would die. The way it was running I thought it may be in the timming with that pipe blueing so badly Any tips..

Thanks,
Guy

Hi Guy
Most anoying to blue a new pipe!
I had a similar problem on my Triumph with twin carbs when a pilot jet blocked with ice..This blued the pipe very quickly.
Chances are you are running lean to get so hot. Your carb is telling you a similar tale as it wants the choke on.
I would check into your pilot jet(blockage?)/idle screw settings first.
Stu.

If you're running a single mikuni, and one pipe turns blue, that cylinder is not getting the same fuel charge as the other. I would check intake valve lash and intake manifold seal. Either you're not getting enough fuel in that cylinder (valve not opening as much) or you're getting too much air (vacuum leak).

Don't forget to make sure the battery is up over 11V. The Boyer runs hit and miss below that and can complicate diagnosis of a carb problem.

Mick

I agree with BillT. If you are running a single carburetor and only one cylinder is running lean, I'd be looking for an air leak between the carburetor and the cylinder head on the side of the lean running cylinder. I'll bet it's leaking between the manifold and the head. Try pulling the carburetor and manifold off, spread some clear RTV on the gasket (not much), re-assemble and let it dry well before starting. See if that does it.

Not checking for retarded timing would be a mistake. Unburnt fuel is as likely the villain as a lean condition. Strobe timing the bike should be the first step as soon as it runs. 5 minute job anyway why not know.

I pulled the spark plug off the blued pipe cylinder and it was black not white like it would be if it was lean but could it be black beacuse of the choke?

Guy

IT could be any one of ten things, working from the inside outward: rings not seated on that side too much oil for a complete burn ,Valves crusted up during the layover needs to run a bit to get them seating properly, again your not getting a complete burn. A bad spark plug, a bad spark plug wire, a bad coil, a bad coil connection bad coil wire. Answer your own question check the timing first with a strobe. A blacker plug than the non blued side would indicate fuel burning in the exhaust pipe. Is it still a points bike, does it still have stock coils, stock grounds,stock carbs.????