stalling/no spark when hot

[MrZoom]

Okay, I have a 1980 GS550E (with handlebars from an "L") that was given to me in sad shape. I have rebuilt the carbs, hunted down all the loose wires I can find, Rebuilt the front brake master cylinder, fixed the choke cable... Basically I am ready to ride. I have a problem that once the engine warms up it wants to stall when idling and does not want to restart. After a 20 to 30 minute cool down it runs fine again. After one incident I cranked it for quite a while but it would not catch. The battery was strong and I could smell the gas fumes coming from the exhaust, but no spark. Is this a common problem or am I missing something obvious?

I really want to ride, but I don't want to be stranded somewhere. Thanks in advance for any help.

[exausted]

hey there
it may be possible you might have a bad coil

exausted

[nabrams]

No spark when hot, soooo:
It could be any of the electronic components (coil, igniter, pulse generator) in the ignition system, or bad connections between them. Any of the above will get worse as the bike heats up, so that the bike will start OK but then die when these get hot.

[MrZoom]

Thanks! I use Accel ignition parts on my cars...are they good for bikes too? Or is there a better (or less expensive) brand? Thanks again.

[t3rmin]

Thanks! I use Accel ignition parts on my cars...are they good for bikes too? Or is there a better (or less expensive) brand? Thanks again.

Most people here go with Dyna electronic ignitions and Dyna or Accel coils (if you want something other than stock coils). A Dyna S ignition is a great upgrade. Do some searching on the forum for lots of Dyna info.

By the way I'm having the exact same problem right now. I have an almost brand new Dyna S installed, so for me it's gotta be wiring or coils...

[MrZoom]

Thank you, T3rmin. Good luck and Godspeed to both of us... not much riding weather left.

[t3rmin]

Well I replaced one coil (the other had been recently replaced already), one plug boot (was shocking me when I touched it), and tested my charging system (per the Stator Papers troublshooting flowchart) so I'm fairly confident of my coils, battery, stator, and reg/rect. There is still plenty of dodgy wiring on the bike, so I guess I just need to go through and start replacing connectors. I found one that was getting so hot it was melting (visible smoke even) through the electrical tape that was on it...

[t3rmin]

YES!!! I think I've got this problem licked. I took the (excellent) advice I read somewhere in the archives and put in a relay and a direct wire from the battery to the coils. The old orange wire (only 10v on my bike by the time gets to the coils) switches the relay on and shoves the full 12+v from the battery into the coils. It idles more smoothly than it ever has and so far there isn't a hint of hesitation/stalling after getting warm (but I need to take a nice long ride to make sure).

I also redid a few semi-fried connectors coming from the reg/rect.

So check the voltage at your coils and try the relay thing if it's low!

[MrZoom]

Congrats! I still need to do some testing, but I hope a pair of coils will keep me riding. For now I just have to keep it idling around 2000 if I need to take it anywhere. I don't know why, but when it wants to stall if I give it more gas it will keep on truckin'... maybe higher rpm means more voltage means overcoming the greater resistance from bad coil means enough spark to keep rolling. I'll keep testing. By the way, having an old spark plug instead of pulling a hot one to test for spark has saved me from cooking my knuckles! I don't recall which member here posted the idea, but thanks!

Later

[t3rmin]

Update: the problem is not fixed. It's better, but it still starts idling rough and eventually dies after riding for 20-30min.

This time I took the spark plug boots off and tested them. 3 out of 4 had no measurable continuity (at least with the voltage the multimeter puts out). Visually, the boots don't look great either. So I ordered 4 new NGK boots from Z1Enterprises and am pretty sure that'll take care of it.

[MrZoom]

Dang, I had some emergencies (furnace going bad) that kept me away from my bike. I let it warm up today until it stalled and then got a spare plug so I could check the spark. Number one had a little spark going on; 2-4 had almost nothing. I'll recheck it later, but I see new coils in my future. I am really glad that your problem is almost totally solved. I hope boots do the trick. Enjoy the ride!

[txironhead]

What relay did you use? Is it available at most auto parts stores?

[t3rmin]

Yeah I just found a generic relay hanging in the electrical section at Schucks. It was labeled as just "relay", as I recall. It happened to have two output terminals which was convenient (one for each coil). I picked up some female clippy ends to match the terminals on the relay and wired it up real nice.

As an update I think my stalling when hot issue is gone for good. After the new plug boots and a vacuum sync on the carbs it'll run all day long. I recently rode it 209 miles in one day (4 hrs on the bike) without a hiccup.

[Thomas Kenny]

This happened to me once on my GS550ES. I traced it to one of the pulse pickups on the crankshaft trigger after getting hot would break contact internally on shutdown. My bike would not start after shutting it down hot. In about 30 minutes the pickup would cool and become operational again. I tested it by pulling the pickups and putting an ohmmeter on them one at a time cold and then heating the pickups with a hair dryer and sure enough the one pickup would trip and I would get a no ohm reading. Might be worth investigating if you have the pulse pickup type of ignition.

Tom