Motorcycle Repair: 84 yamaha 700, exhaust leaks, yamaha 700

Question
We spoke just acouple weeks ago about the bike. I have an 87 yamaha xv700L This is the one that blows cold exhaust out of the front cylinder.
compression test 150 in each cylinder, and holds pressure. The carbs have been done, new coils,plugs. I have noticed that I will have spark at idle  only,(wire just held next to plug) when the rpms advance the spark comes cojpletely to stop. All exhaust leaks fixed no more backfire, time marks check. Could this problem be from the T.C.I. or the generator sytem, or wrong battery. I am really reaching for to figure something out. Can you tell me if the t.C.I unit J4T00871 mitsubishi (84 xv700L)
Can be swapped out with the J4T00671 mitsubishi (81 xv700). Any help is greatly valued once again thanks.

Answer
Hi Mike,

I suspect the TCI is not working properly. It is important to have the battery, too, but this won't cause the spark to stop.

Very good cylinder compression.

Don't have a cross reference for the TCI part numbers. There are differences between the parts, but only Yamaha knows. It could be as simple as how the part fastens to the frame (shape).

Try websites dedicated to your MC. Some have tech forums. Someone may have experienced the same problem.

Respectfully,
Mark Shively