Motorcycle Repair: 1978 XL350 quit running, xl350, permanent magnet

Question
Hey Bill,
I'm working on a 1978 XL350 single (sn 3204625) which I recently bought. When I got it, it ran poorly at best. It would run for a short time,5 to 10 min. then quit. Now it won't start or even try. There's no spark at all.

Mike

Answer
Mike, the XL350 has a spread out magneto ignition which requires:

Permanent magnet rotor, spinning inside a set of windings (or over them)

A set of ignition points to help saturate the coil and time the collapse of the magnetic field and a condenser to absorb the excessive EMF when the points open up carrying all that stored energy.

Ignition coil to fire the spark plug.

The things to check are: Cleanliness of the point contact faces. The gap should be around .014"-.016" and they should open at the F mark alignment of the rotor and stator markings.

If points are clean and gapped properly, the problem could be a grounded primary ignition coil, open wires in the ignition circuit... or grounded wires in the ignition circuit. If the condenser fails, you will get a random spark, generally.

Be sure that the ignition switches and KILL switches are all functioning properly. Both KILL and IGN switches will ground out the ignition system to shut off the engine. Otherwise, the ignition is self-powered, as soon as you turn the motor over.

Try a new spark plug when testing the ignition system.

Be sure that the fuel system is clean and venting through the gas cap properly. There is a screen in the petcock which should be checked. Carb jets and passages should all be clean and fresh fuel put in the gas tank.

Illustrations for your bike can be found at www.cmsnl.com

Bill Silver