I rode my '30 101 around 20 miles, it performed faultlessly, then would not restart.  Still no start after I let it go cold.  It'll fire once on one or two cylinders, but that's all.

Because of recent work I know the carb is OK.  The Splitdorf S is sparking, but slightly more yellow than I'd like. Clearances are OK.  Throttle, choke, retard have no effect on the starting.

Mags usually fail when hot, so I'm surprised by the suddenness of the failure, and am struggling to trace the issue. Can anyone point me in the right direction?  I need to bubble test, but would be surprised if I found anything as it went from perfect, easy starter to no start in such a short time.

Also, I'm not familiar with the S model Splitdorf, what is the purpose of the carbon contact under the cap, and should it be springloaded to touch the rotor?

Thanks.

Electrical problems are usually immediate while carb /fuel problems can be spasmodic/spluttering etc., unless jet in carb blocks up. Good idea is to have fuel tap with built in gauze filter.

For spark testing I have a simple device shaped like a sextant, so that the spark gap can be varied when it is inserted between spark plug and the HT lead.

Not sure if you can still buy these but I will check on line.

Mike.

Spark disappearing as bike warms up, then restarting after it cools down is usually a faulty condensor in the magneto. Old brit days it was not uncommon to "water the mag" to cool it down and get you home. I have done this on occasion.

Had a similar problem on a KLR and a 79 Triumph, both with electronic ignition, the pick up units break down under heat when old, and cut out when hot, often times will work until eather gets up to hot sunny August days. Tested ith a heat gun and a resistance tester, as the temp rises, al of a sudden the resisitance will rise and then go to infinity.

Tim