1980 GS850 dies when hot

[mattd1205]

My 1980 GS850 recently developed an issue where it stalls out but runs perfectly otherwise. The first time was when the bike was restarted after a 25 mile freeway jaunt. It ran fine until it suddenly lost power and wouldnt restart until a few minutes later. The second time was at a stop light after riding for 15 minutes or so. third time the bike sat again for about 10 minutes after a 20 minute ride. The bike restarts every time after letting it sit for a few minutes. I pulled the gas cap to see perhaps it was venting the gas tank but it made no difference. starter always cranks the bike over so I doubt its an issue with the kill switch. Ignitor perhaps?

Thanks
Matt

[JTGS850GL]

Best advice I can give you is to verify no spark when it wont restart. Sounds like the problem is reproducible so that makes it a little easier to narrow down. If you have spark but no fire then that will point you in another direction.

[Nessism]

What maintenance have you done?

[mattd1205]

What maintenance have you done?

Engine had top end refresh about 1500 miles ago which consisted of new rings, cylinder hone and a valve job. I have checked the valve clearances twice since then and changed the oil 3 times. new plugs 500 miles in. 140 PSI of compression across the board as of two days ago. The regulator/rectifier and stator was switched with a caltric units close to a year ago.

Matt

[stetracer]

Sounds like your coils are going bad they tend to stop working when they get hot

[mattd1205]

Sounds like your coils are going bad they tend to stop working when they get hot

I was thinking that but the engine doesn't fire at all when it stalls out. from what I understand the bike will run (albeit extremely roughly) on two cylinders if one of the coils fails. The bike doesn't fire at all when it's doing its thing. Is it possible that both coils are failing?

[Crankthat]

Without other symptoms.
In all truth it could be many things.
Probably not the problem.
Still a possibility.
Great maintenance that you should be doing anyways.

I would check for heat damage throughout harness mostly at connections.
Do not forget the mess inside headlight bucket.
You could simplify by concentrating on ignition system wiring.

On a GS you will find many things needing addressed.

Chances are you will find some areas with damage from previous problems.

Even a loose connection in the wiring slowly heating up.

Fuse holder heating up with current spark jump.
If you are using the glass fuses then a great chance of this being a problem.

Clean, replace, repair.
Mark these areas with colored tape, zip tie, or possibly a wrapped wire bag clincher.

If the problem persists check the areas marked for heat as soon as you can before they have a chance to cool down.

If you find nothing then move on to any other ideas put forth here.

Keep us posted.

[tom203]

I was thinking that but the engine doesn't fire at all when it stalls out. from what I understand the bike will run (albeit extremely roughly) on two cylinders if one of the coils fails. The bike doesn't fire at all when it's doing its thing. Is it possible that both coils are failing?

Both coils failing is unlikely, but trigger signal from signal coils or ignitor itself could be messed up causing neither coil to fire.The ignitor is fed by same orange/white wire that leaves kill switch and connects to ignition coils. You need to determine if this still has 12 volt positive during a no start condition,

[850 Combat]

Does the starter spin just fine when it is stalled? I think that is what you meant.

If so, would agree that you likely have an ignition problem, and that it is likely upstream of the coils if so. If you have the "coil relay mod", I would look there. That is a common result of that common band-aid. Beyond that, I would change out the ignition module next. I think I've got one in my garage in Maine, but I won't be there for a pretty good while. I have had failure modes with coils, condensers, Fuel Injection ECUs, and relays which only manifested themselves after 30 minuets to an hour of use. Who knows. Maybe its a fuse going bad. Change them all. (I have found that if one goes, the others will later).

You might also bring a volt meter with you and test when it isn't working. You may consider pulling the tank and letting it run with a fan on in the driveway to see if it can fail without stranding you.

Good luck.

[JTGS850GL]

Like I said above... If you can reproduce the failure mode then do it and then troubleshoot why you have no spark. That's assuming that you even have a spark issue. Can't fix it when it's not broke. With that said, you might want to start by boing through all the connectors from Signal generator -> Igniter -> Coils and verify good voltage on the orange/white wire. Could be so many things that you'd be shot gunning parts for quite some time before you stumble onto what's causing the problem. Quite expensive to do it that way as well. Be thankful that you don't have an intermittent problem that can't be reproduced. Those will drive you nuts!!!

[mattd1205]

Like I said above... If you can reproduce the failure mode then do it and then troubleshoot why you have no spark. That's assuming that you even have a spark issue. Can't fix it when it's not broke. With that said, you might want to start by boing through all the connectors from Signal generator -> Igniter -> Coils and verify good voltage on the orange/white wire. Could be so many things that you'd be shot gunning parts for quite some time before you stumble onto what's causing the problem. Quite expensive to do it that way as well. Be thankful that you don't have an intermittent problem that can't be reproduced. Those will drive you nuts!!!

Ok, I finally got time to work on the bike today. I replaced the ignitor and same issue. Ran ok until parked for an hour, restarted and it died a few hundred feet later. I pulled the boots for cylinders two and four, held them close to the engine and verified there wasn't any spark on any of the cylinders. I'm gonna break out the multimeter and start ruling stuff out

[OldVet66]

When I first got my bike I made two mistakes that resulted in the same symptoms. I used the wrong type of fuel line and put a fuel filter in the line. When the bike got hot, the fuel line would soften up and kink shutting off all fuel flow.

[Redman]

[QUOTE=mattd1205;2175553].....verified there wasn't any spark on any of the cylinders. I'm gonna break out the multimeter and start ruling stuff out[/QUOTE

Check the signal generator.
That would be my suspect of what kills all spark after the engine warms up. (especially since you have swappwed the ignoitor).

Wheerever you got the igniter as a test, can you get the signal generator too?


You have a manual that shows the signal generator test? THe check is an ohm test.
And ther is a way to disconnect the signal generator, and simulate for it as a test of the remaining entire ignition system.

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