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Engine dies

  • Thread starter Thread starter glenwill
  • Start date Start date
G

glenwill

Guest
My 1980 GS550L has developed a problem. I'm posting in electrical, as I suspect that's where my problem is, but I don't know for certain.

The bike has otherwise been running great. I did a full carb disassemble, soak, clean, etc and synced the carbs. I did a charging test, and I have a good charge. I have a digital voltmeter on the handlebar, and it shows around 14.4 volts when riding.

So the problem is that after riding for a bit, I'll pull up to a light and come to a stop, and the engine will just die. No sputter or delay, just like it was unplugged, so to speak. When I go to start it back up, the starter sounds strong, but the engine won't turnover. If I pull over, play with the choke, throttle and starter for a bit, I can get it to turnover. Once it turns-over it will usually start right up, and then it will run fine for miles. Sometimes it will die again at another light, sometimes it will not. It never dies while I am riding, only at idle. My idle, which needs to be adjusted down, is just under 2K, so it's not like the idle is too low.

I suspect that the problem is electrical because it dies so suddenly, and that after a few seconds of trying to start it, whatever the problem is has resolved and it starts up.

Anyone have any direction on where to start testing to figure this out? Am I looking in the right place with ignition/electrical?

Glen
 
"When I go to start it back up, the starter sounds strong, but the engine won't turnover. "

I assume you mean that the engine turns over, but doesn't come to life. 2k idle is too high,so I'll guess your idle circuits are not fully cleaned out (or adjusted right) so engine is mixture starved after warmup. At the light, carbs fall back on the idle circuits entirely- not enough mixture here, she dies.

how far out are the mixture screws?
 
That same thought crossed my mind.

If the mixture screws are less than two turns out (from lightly seated), turn them out to THREE turns and try it.

If that seems to help, slowly turn the mixture screws IN until the engine slows down a bit, then turn them back out 1/8 to 1/4 turn.

You should be able to idle close to 1100-1200 RPM.

.
 
Thanks, I'll adjust idle and report back. I think it's just high because my son adjusted it when the engine was cold and he thought he needed it higher. I'll adjust it back down and see if it holds idle, and if not adjust the screws.

Glen
 
So I didn't have a lot of time to troubleshoot, but I did start up and adjust idle. When I had previously stated my idle was 2K, that was based on what I observed in my last ride. However, starting up and letting it warm up on Saturday, the idle settled in around 1,400. I adjusted it down to 1,200, and it held fine for the 15 minutes or so that I let it run (with a fan cooling it).

I suspect that after riding for a bit is when the idle creeps up, and when the stalling problem develops. I'll take it out for an extended local ride this week and see how it behaves.

Glen
 
I think the 80 GS550L has rubber carb boots with O rings. I've read that bad O rings can lead to a high idle after the bike gets hot. Hope one of the experts can confirm.
 
Thanks Jordan. It does. I replaced all four boots and o-rings 2 years ago when I reconditioned the bike.

I just checked, and all four boot clamps are in tight too.
 
I got a lucky break today, and had the no-start/no-run condition while sitting in the garage. I tested for spark, and none of the plugs has spark. Thinking this might suggest the signal generator or ignitor, I reached under and wiggled the cable running from the signal generator to the ignitor, and then it started right up.

Thinking this meant a broken wire or loose connection, I unplugged the signal generator from the ignitor, and pulled the cable back through the frame, so I could plug it back in with the whole wire exposed. No amount of wiggling or pulling on the wire or connectors would make it fail. None of the wires looks cracked or badly bent where it might have broken. I suspect it may just be corrosion build-up on the connector to the ignitor.

I see there are some tests for the signal generator. I'll run those and make sure it is good. If everything checks out, I'll put some ox-guard on the connector contacts, and take it for a ride.

Any other suggestions?

Glen
 
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