81 GS850 kills once it warms up.????

[nisom512]

Hey all.

I was wondering why my bike is killing once it warms up. I know the reason is warming up because it runs just great idles great, it doesnt waver up and down. Air box great and sealed with Uni filter(oiled), intake boots good no leaks, carbs rebuilt the right way and with o-ring kits, intake boot o-rings, new battery, new R/R, valves adjusted, oil changed(with filter), new coils(not sure how new bought bike with them they are Accel brand), runs and drives but here is the catch. I start it, then let it sit for a bit with the choke on for about 2 min then I back out and drive off. but I can only get about 3 blocks and it will just kinda slowly kill out. it starts to get non responsive and then eventually kill.

Also ryonker and I were working on it tonight and both came to the conclution that it was killing out once warmed up. We were trying to sync the carbs just because we wanted to see if just maybe. but every time we let the bike run for more than 2 min and were trying to balance it would eventually do the same thing just kill out. so.....we would wait for about 5 min with the fan goin on it and it would start up and run for about 1 min and then kill again. and the thing runs just great so I dont know what it is.

Oh and after my 3 block drive we checked the plugs and from left to right 1=really lean(White)
2=really ritch(Black)
3=really lean(White)
4=mildly lean(grey)

I also have aftermarket 2 into 2 exhaust with baffles, its been rejetted from stock to 42.5 and 122.5.

So my question is. Is there somehting on the bike that would kill once the bikes warms up?

and why would the #2 cylander be so rich?
I tryed adjusting the mixture screw and the #2 got better but the #1 and #3 didnt really.

Any advise is really helpful

Thank you
Jake

[almarconi]

Since your problem happens when the bike gets hot it would lead me to suspect one of your electrical components, rather that a fuel related problem.

What is the condition of the stator? Are the coils getting hot when this happens. Is the ignitor getting hot?

I wouldn't draw any conclusions yet on the rich/lean conditions of the engine until you can get it running on a consistent basis.

[Nessism]

Hey Jake,

Rich #2 could be fuel dumping backwards down the petcock vacuum line. If you have a piece of clear tubing you might want to try that to see if there is fuel in the line.

Regarding the bike, sounds like you are running your float bowls dry. Could be bad petcock, vacuum leak from a bad gas cap or something wrong with the floats (unlikely).

You might want to try the bike and next time it craps out open the gas cap and listen for suction, which means the tank is not venting. If that seems fine, as soon as the bike craps out remove a couple of float bowl drains to see if there is fuel in there.

Hope this helps.

[almarconi]

If it was fuel related, why would the bike restart and run when it cools down and cut off when it get hot?

[Nessism]

If it was fuel related, why would the bike restart and run when it cools down and cut off when it get hot?

Petcock could be restricting flow. Running the bike drains the fuel and petcock can't keep up to fill the float bowls. Running the bike on Prime might answer some questions as well. pull off the fuel line and check to see if you get full fuel flow when in the prime position first.

[ryonker]

I was working on the bike with Jake. When we were trying to sync the carbs, we were running it off a satalite gas container and it was doing the same thing...killing after it ran a little while. Then after it sat for a minute or two or three it would start up just fine. The engine sounds great and seems to run really well and then just starts to die and then kills.

Rick

[Nessism]

Is there a fuel filter in the fuel line? Again, be quick next time and remove a couple of float bowl drain screws and look for gas in the carbs. If there is gas, pull a plug right away and look to see if the plug is wet or dry, also check for spark. Work fast after it craps out and check stuff. If it repeats the problem, you should be able to chase it down.

[nisom512]

Petcock could be restricting flow. Running the bike drains the fuel and petcock can't keep up to fill the float bowls. Running the bike on Prime might answer some questions as well. pull off the fuel line and check to see if you get full fuel flow when in the prime position first.

When we were trying to sync the carbs we were using a separate tank with clear fuel lines and rick has used it on CV carbs before I beleive. but there wasnt a hook up for the vacume line. but even so the bike did the same thing with the bikes tank on or off so I would have to reject the conclution of the petcock and tank venting. I was really thinking it was an electrical. but again I could be wrong.

Thank you guys for the quick and great responses Please keep them coming.

Jake

[ryonker]

Is there a fuel filter in the fuel line? Again, be quick next time and remove a couple of float bowl drain screws and look for gas in the carbs. If there is gas, pull a plug right away and look to see if the plug is wet or dry, also check for spark. Work fast after it craps out and check stuff. If it repeats the problem, you should be able to chase it down.

In my Satalite gas system there is a fuel filter. Still seems to flow ok though.

Are you thinking one or more of the carbs isn't getting enough fuel and that causes it to kill?

[almarconi]

Are the coils getting hot when this happens. Is the ignitor getting hot?

Well..are they overheating?

[KEITH KRAUSE]

Regarding venting, be sure your temporary fuel reservoir is vented. Be sure the gas cap venting is clear. Compromised venting WILL result in fuel starvation exactly as you describe.
As stated earlier, you can immediately check for fuel as it dies. Remove floatbowl drain screw(s) and see how much fuel comes out and compare.
I also wonder about the black plug/cylinder you have. If the bike is in otherwise decent tune, including proper idle rpm, the bike will not die when running on 3 cylinders due to a fouled plug. But if black, then you're getting poor combustion which must be fixed. Determine if the black plug is fuel mixture or oil fouled. Test for good bluish spark before start up and after it dies.

[nisom512]

Regarding venting, be sure your temporary fuel reservoir is vented. Be sure the gas cap venting is clear. Compromised venting WILL result in fuel starvation exactly as you describe.
As stated earlier, you can immediately check for fuel as it dies. Remove floatbowl drain screw(s) and see how much fuel comes out and compare.
I also wonder about the black plug/cylinder you have. If the bike is in otherwise decent tune, including proper idle rpm, the bike will not die when running on 3 cylinders due to a fouled plug. But if black, then you're getting poor combustion which must be fixed. Determine if the black plug is fuel mixture or oil fouled. Test for good bluish spark before start up and after it dies.

It was black at first then I monkeyed with the mixture screw and the plug was less black.

[nisom512]

Well..are they overheating?

if you tell me where the igniter is I will test this.

[almarconi]

if you tell me where the igniter is I will test this

Under the right hand side cover.

Put your hand on the coils and see if they are hot after the bike is running for a while.

[nisom512]

Under the right hand side cover.

Put your hand on the coils and see if they are hot after the bike is running for a while.

but the bike doesnt run for a while it will stay alive for about 4 min. if that today I couldnt get it to stay alive for more than 2 min so now I am really confused but if I can I will try and see if the coils get hot.

Jake