Surging and rough running

[Guest]

Had something odd happen to me today on a ride and I don't even know where to begin searching here. If there's a thread on this somewhere please just point the way.

I was out for a 50 mile ride today on my 80 GS550. After about 30 miles into the ride I was coming up a hilly road and I noticed the motor start to surge a touch (was doing about 50mph). I downshifted and tried to give her a little throttle and there was nothing. The motor seemed to be leaning out. Turning off the road to investigate it quit on me. It seemed odd, I've never had an issue with this motor before and it was puzzling. A quick check over the motor at the obvious things and nothing seemed out of line. Half tank of gas. Motor didn't seem abnormally hot or anything. We let it cool for a few minutes and started it up. It kicked right away but stalled after 10 seconds or so. Let it sit a few more minutes and started it up with no hassle.

After getting back on the road I got about 5 miles from the spot that I was at before and I noticed the motor start to surge again a bit (was doing about the same speed). As soon as I turned off the road on a side street it died on me again. For whatever reason as I was rounding the corner after it died I put it in 2nd and dumped the clutch and it refired but was running like crap. Almost like it was running on 2 cylinders. I revved it up a bit and it seemed to come back to life and run normally. Got back on the road again and rode it about 18 miles back home with no issues.

I'm a little perplexed. Anyone have a thought on this?

[chuck hahn]

Check the signal generator under the right side engine cover. Dirty, bad wires. corroded wires... sounds like once shes getting heated up its causing an ignition failure somewhere. Harness connectors at the coils clean?

[Nessism]

First guess is a failing petcock or the fuel cap vent is getting plugged up. Hard to say. Needless to say though is you should make sure all the bikes maintenance is up to date such as: valve adjustment, air filter cleaning, fix charging system wiring, check voltage at the coils and clean terminals as needed, etc. You can't diaganose running problems on a bike that needs maintenance.

[chuck hahn]

Let it cool and start with an auxiliary bottle and feel the coils to see if they get abnormally hot. They will get pretty warm but youll notice if they are super overheating!!

Do your caps have the resistors in them or non resistor caps? I always eliminate the resistors and replace with a piece of brass or copper rod.

[JTGS850GL]

Pull the plugs and see what they look like. They may be carbon or oil fouled. If they're white then maybe a lack of fuel as in clogged petcock. As others have said, check all your connectons and verify voltage to the coils as well.

[Nitronate]

The petcock is an interesting suggestion. I had another problem before where the bike seemed to be hard to start after sitting for a week or more. Almost like the fuel had drained out of the carbs and it took forever to refill them.

I wonder if they are related problems.

[blowerbike]

never seen a bad trigger plate unless it was wrecked.
they are just magnets...

[JTGS850GL]

Check to see if the float bowls are full and see if the problem goes away in the "prime" position.

[Nitronate]

Check to see if the float bowls are full and see if the problem goes away in the "prime" position.

I didn't think you wanted to leave it in Prime for any long period of time. This started to happen 30 miles into a ride. Would it be ok to leave it in the prime position that long?

[JTGS850GL]

As long as the engine is running, there's no difference between prime and run. The issue with leaving the bike in prime is when the engine is not running. If one of the needle valves fails you can flood the engine with fuel.