Norman1950
XS400 Addict
If your battery is charged, the sounds like the starter relay is not working. Or if the battery is close dead, it isn't giving the relay enough power to turn the starter.
When I first fixed mine up it puffed a bit of smoke off. It could be the rings, the valves, or the head gasket. Ride it more before you go nuts chasing it. I had all kinds of problems just because the bike sat for so long. I had low compression because carbon was causing the rings to get stuck in the pinched position instead of expanding, so you never know.
If you've been screwing with the bike a lot and just letting it idle without running it your battery might be low. Make sure the bike is charging and check your battery.
Good idea. I think someone told me at one point that if you're riding for less than 30 minutes give or take the battery is likely not getting charged very much or is only being drained. The old charging systems on these bikes are not that strong and they don't really charge at all at idle; you need to keep them above 2,000 rpms or so to really get some action! An intense trouble-shooting session in the garage with lots of idling and starting using the electric start will kill your battery in no time.