1980 r80 backfires and dies

[sinjun68]

Hello All,
So my buddy was riding along on the highway, and suddenly his r80 loudly backfires a few times and dies.
Coasted to a stop. It's now at my place. Power to lights, and gauges but no power to ignition. What should we check first, and what might this be a symptom of?
Thanks!
-Chris

[dwerbil]

Welcome Chris!

I've had this sorta happen a couple of times to me on my R100/7. Once was when the mechanical advance nut came loose and the advance pulled off a bit from the ignition points, and other time when rain water, during hours of riding in a downpour, entered the points area and fried the points.

When you say no power to ignition, does that mean to the coils, condenser or points?

Also, what exact year/model is your friends R80?

[sinjun68]

Some updates! First, the bike is a 1980 R65 (not 80) The bike was in an accident last year with damage to instrument cluster. The oil light is the only light that (occasionally) works. The Generator light does not work.
I put new battery on, and bike starts, and runs as usual. I put volt meter on batter and reved engine. No increase in voltage. Bike does not seem to be charging. Is the Generator light part of the charging circuit? If so is the fact that ist no longer works keeping the battery from charging?

[dwerbil]

Fix the generator bulb/circuit and it may fix the bikes charging problem.

[SteveD]

Fix the generator bulb/circuit and it may fix the bikes charging problem.

Gotta start there. Here's a thread of collective experience that looks at charging issues. Hopefully it provides further clues.

viewtopic.php?f=1&t=1629&p=18876&hilit=rotor#p18876

[Roy Gavin]

I had a similar backfiring / cutting out problem - it was poor contacts in the ignition switch.

So try waggling the key,and the back of the switch, to see if you can get a flash of power to the ignition.

[sinjun68]

She's running fine but not charging the battery. It is definitely the lack of the generator light. The circuit board in the tach side of the instrument cluster where the generator light was, is broken in about 6 pieces. The housing itself is pretty broken up as well. sockets for a couple other lights are severed as well. Looks like a new cluster is in order. Dang they are pricey!!! I'll do some research to see of a way to bypass the generator light or put a temporary inline light in to complete the circuit so he can ride it a bit while we source a reasonably priced used cluster.
Thanks for the help folks!
-Chris

[dwerbil]

You might find a used instrument cluster housing from Mikey at Martindale Cycle Works. Course too, try Matt here at Boxerworks. You can find his email here on the forum in the members list.
If your friend intends to keep his R65 for a long time, I'd buy a new circuit board. For my /7, I spent about 55 bucks for one a few years ago.

[montmil]

As noted by others, the GEN lamp is critical to keeping the battery charged. That little bulb's filament serves as a resistor and the exciter for the alternator. Check Snowbum's site for an easy DIY replacement circuit that bypasses the GEN bulb circuit and allows the alternator to function. Kind of a belt and suspenders deal. I have fitted these simple in-line resistor circuits on both my '81 and '83 R65s. The '81 has a digital gauge with the OEM gauge cluster removed, whereas the '83 keeps its good condition instrument pod.