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1981 R80G/S 180K miles
I haven't been here for a few years, but the bikes are still the same. Started off this morning for a quick trip to Mexico before the snow comes.. Got 15 miles and the bike quit. No spark at plugs when shorted on cylinder. But I got a single spark when turning ignition key on and off. I had similar response on an R65 years back, so thought my ignition canister had failed. I carry a spare, so replaced and bike started fine.
But I returned home because I wanted a backup for my backup. At home I put the failed canister back on and the damn bike started and ran fine.
So now what? Maybe not the canister in the first place? Black box? Temp was in the 50's this morning, so shouldn't be a heat related issue in 15 miles. Bike rode home fine with replacement canister, so if it was black box why no second failure?

Any nuggets of wisdom?

Dirty connections, cleaned while changing cans.
Guy

Could be temp related. Internal connections getting larger with heat expansion. I had an aftermarket ignition do this. At first it just seemed like a wiring issue. It would have issues sporadically. Then it broke down 6(very long pushing) blocks from home. I pushed it home, attempting to start it many times. When I got it to my garage (panting, sweating and swearing) it (of course) started right up. My guess was that it would fail when it reached a certain temp and would then need to cool down quite a bit before it would function again. I replaced the magnetic sensor, and it's worked just fine since. It was a lucky guess.
Are you riding to Mexico from BC? Get a list of Airheads along the route that could come to your aid. Prepare for a break down and it won't happen.

Thanks for the responses. I don't think it is temperature related as it was a cold day, and really I had only gone 15 mile, barely got the bike warmed up.
I cleaned up all the canister connections (although they looked good), checked an re-seated a few other ignition related connections .

But thinking further....
Will start off on my trip in the morning and see what happens. I guess it could be an impending coil failure, related to a bit of moisture (air was damp) . The bike started after I replaced the canister, but maybe that was irrelevant, maybe it was the time delay it took me to make the exchange that was the deciding factor.

I got home (but it was the same return distance), maybe if i had ridden another 10 miles the ignition would have failed again. Or maybe not, the sun was out by then and the air was drying.

I am thinking I better take a coil off my wife's bike as a backup.

Yeah, if you've got a donor there, that's the easiest way to eliminate possibilities: by trading in known good parts.

Good luck. Intermittent problems are always the worst, but if you can get the problem to appear with any consistency, it will be pretty easy to figure out.

Seems like I recall on the "80's bikes with electronic ignition there is a problem with the coil...it gets cracks and then dampness spoils it. These are the "potted" coils, not the old-fashioned ones that look like cans.
It might be that.
Do you have a capacitor in the circuit somewhere??????
(everyone ELSE knew THAT was coming)

Jean wrote:Seems like I recall on the "80's bikes with electronic ignition there is a problem with the coil...it gets cracks and then dampness spoils it. These are the "potted" coils, not the old-fashioned ones that look like cans.
It might be that.
Do you have a capacitor in the circuit somewhere??????
(everyone ELSE knew THAT was coming)

Yes, I have the 'potted coil' and know about the problem with the case cracking. There is some hazing on the end which is why I am thinking along these lines. Realized I can't take the coil from my wife's RT as although it is '82 it still uses the double cans.

And a capacitor in the circuit, I have no idea. This is not something I know about. Guess I better do a search.

OK, searched a bit. Don't think there is a capacitor on the post '81 machines. If there is I can't visualize seeing it. My '78 RS has one because it started with points.

No capacitor in 81 G/S, unless converted to points-in-beancan.

On the road and no further problems. So I am assuming my problem the other day was dampness and a flaky coil.
I borrowed one off my daughter-in-laws R65. This bike used to be my wife's and I put the coil on back in 1995 (bought used then) so I know it is good. Got to love 'airheads' for their longevity. Have ordered a new coil from Rick Jones delivered to AZ, so will be good to go totally in 3-4 days. And at a cheaper price than I paid for the used one back in '95.

Thanks for the helpful comments.

Cervesa here I come.