Hello
My standard M20 (1943) starts easily and runs sweet for about a mile before it misfires badly and I have to limp back home. Plug colour light grey.
It Sparks well and fuel gushes out of the pipe. Have put spacer on carb manifold but that made no difference. Any ideas? Cheers!
Magneto problems once it has warmed up or the carb is running out of fuel.
The one mile ride before it runs bad, is the motor cold or hot? If you touch the magneto, does it feel hot? If the magneto is still cold, it's probably not the problem.
When it runs bad and you park the bike, how long does it have to sit before it starts and runs OK?
Does the motor bring hot or cold before you ride it have any effect?
Does it do this every time you ride the bike?
My guesses are either the mag is failing when it gets hot due to bad windings or bad condenser.
Or, the fuel tank is not venting properly and you are running out of fuel.
Thanks Bruce, after running from cold the motor warms up quickly but the magneto is only warm. The vent was clear and I ran it with the fuel cap loose to test.
It behaves in exact the same way every (short) ride now! It starts relatively easily when hot
I think what Rob is eluding to is, you can't fit a standard condenser without a total rewind. Also are you pulling the choke lever towards you for "Choke Off" (Silly question but I've seen it often.:thinking_face: Ron
I agree with Rons thinking. Have had a spate of people here in Australia recently running with choke on. One guy got real cranky with the engine rebuilder as it was struggling up a slight incline. Calmed down when told he was using the choke wrong.
It's always difficult when there is a newish poster. None of the regulars have any idea of experience level. The idea of pulling a choke off rather than pulling it on often seemed a little odd to the majority who first saw chokes in post-war cars.
Andrew
About this choke thingy.
I'm not sure whether you know all this, apologies if you do.
Take the air filter off, (if there is one) & move the choke lever one way & the other. You'll see the choke slide moving in the carby bore & will know whether it's open or not.
