XS400 Member
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West bend wi
Hello I am having an issue with my 1983 XS400R Seca. I road in the morning, the day after my bike had been in the rain, to work with no issue. When I was about to head home, I tried to start it and it turned over fine but wouldn't go/catch at all, just endlessly turn over. Figured out there was no spark while it was cranking on either side, but curiously I would get a big spark when I put the killswitch to off while the key is on. So much so that while cranking and then quickly hitting the kill switch would cause the pistons to briefly fire. Also, weirdly the turn signals don't flash anymore as they normally do, they just remain solidly on when switched. No idea what that is about.

I tried several things, cleaning the ignition switch, charging the battery to full, new spark plugs, etc. Nothing seems to fix it, I would suspect the TCI, but I had replaced that a few months ago when I was having problems with only one side firing. Based on this, I am now assuming there is a short somewhere in the wiring, because of the bike being in the rain the day before and perhaps corroding something. Is it possible the ignition circuit is crossed with the turn signal circuits? I think the relays are working correctly because they make a loud clicking noise when the key is turned to on and the kill switch is turned to on.

Does anyone have any ideas, is there any resolution to this problem? Should I try to clean the key switch as well? Continue testing for shorts? I'm a little lost here, as all of the components appear to work, the spark is strong enough to fire the cylinder but it just doesn't go at all while cranking
When two different, unrelated circuits start acting up at the same time it usually points to a low battery (already addressed, +1) or a bad ground. Since both circuits are in the handle bar switch gear, try concentrating there by cleaning up contacts, tracing wires and cleaning up any plugs on the ends. You might look for ground points on the bike and give those some extra attention as well.
So, how ignition coils work is that there is constant power to them, and to produce the spark the ground side gets disconnected. That's what breaker points do - they break the connection. On an 83 it should be the igniter (TCI).

The hot to the coils runs through the kill switch. When you flip it, you are pulling power from the coil, and that's why it produces spark.

Look at the wiring from the coils to the TCI - if there is a short to ground there somewhere, that would do it. I would also unplug the TCI and look for corrosion in the connectors. Clean it out.

When you replaced the TCI, what did you replace it with? If you got a used one, you still have a 40 year old piece of electronics. Nothing says it can't up and die on you.
Probably worth testing the trigger coils also- one of mine had a problem where it would open when the engine was hot leading to no spark. A lot of the signals worth checking are on the TCI connector, as shown in the service manual.