Mister B

For anyone else who runs into this problem, it ended up being one of the pickup coils. Yamaha no longer makes replacement units but if you can get a hold of a pickup unit from a 650 you can butcher it and splice in the coil(s) as needed. As soon as the coil was replaced the bike started right up.

I was hoping they would be the culprit, but i tried running the bike without the caps, just straight wire on plug and got the same result, left fires sporatically, right fires fine.

Hey Gdarrel, I am having THE EXACT same problem with my 82' SECA, went through the same diagnostic paces as you and finally found that the left plug is getting an extremely weak spark. It fires once if at all at random when cranking the engine while the right will fire multiple times in the same time frame. Did you ever solve the problem with your bike?

Just got my hands on an 1982 400 SECA, and the bike will not start without help from starting fluid. Carbs have been cleaned, new plugs, wires, and replaced coils. Engine has compression, and there is gas making it to the combustion chamber. Ive found that the right plug fires many times as the engine is cranked, but the left plug fires once, if at all, with multiple strokes. The bolts holding on the crank cover on the left side are starting to strip, why didnt yamaha use regular bolts, so right now i havent been able to check the pickup coil. Has anyone else come across this problem? Its down to the ignitor box and the pickup and im looking for some guidance before I start replacing parts. Any help is much appreciated.