'84 R100RS Charging system/Running issue

[Kurt in S.A.]

But the problem doesn't exist if the charging system is disconnected...isn't the tach still running in that configuration? The tach's on the ignition side, not the charging side. The tach is just a single-ended output/reading...I can't see how it feeds back into the ignition system.

Kurt in S.A.

[barryh]

OK I forgot he said that although he didn't say how the charging circuit was disconnected. If by some chance it was pulling the multipin connector on the instruments then....

My logic for speculating that the tach could have the potential to kill the ignition is that if it fails so that the impulse wire is short circuit to earth the ignition will not fire.

[Snakeoil]

Good discussion guys. Thanks very much.

I'm getting good input both here and from the guys over on the BM Riders forum. One theory that has been put forth is the HES is "flakey" and when the alternator kicks in the increase in voltage is killing the HES.

I also want to point out that I'm not the guy working on the bike. I wish I were because this is an interesting problem. But the bike is in my friend Lance's shop, which his 2 hours from me. I've been funneling the info to him as it comes into me. He's 76 and has lots of stuff going on this time of year in addition to bikes that come into his shop. So I'm not sure when I'll get feedback on anything he checks out. I will eventually talk to him, but not sure when he will dig back into the bike.

I did not want you to think I was gathering info and not providing feedback.

Thanks and regards,
Rob