1980 xs400 After 20 min left cylinder gets no spark

[Capt Slow]

I was riding on the highway yesterday and after about 20 min I noticed the bike hesitating and then sputtering. It was running on one cylinder. The left cylinder had no spark. Verified this by disconnecting each spark plug wire. This morning it ran fine. This has been happening for a while.

Any ideas?

 

[corruptmind]

Swap your coils and see if it still does it on the left side. If it does its your tci getting hot and giving out, need to have it repaired or replaced. If it switches to the right side its the coil, replace it.