Idles and rides great for a while then starts stalling at stop lights after 20 min.

[tsunamimike]

Alright so the beast is back together.. 81gs650gl, starts fine, runs well without stalling etc., 20 minutes or so after riding around stopping at liughts etc.. then bam, the idle goes under 1100, and eventually stalls out. Get it back running ride to the next light and then it seems fine rpms at 1000. Then the next light it goes and almosts stalls <had to rev it manually> , what the heck? When we took it apart noone touched the carbs at all, put everything back on it and it just isn't idling the same, had to mess with the screw under the carbs <have no idea what it does> but it raised the rpm periodically.

What do you think?

[Craiger]

Lean? Did you increase the air intake?

[Craiger]

I just noticed you were having carb problems in previous threads. You state that nobody touched them....are you still having a stumbling problem with one carb?

[tsunamimike]

i dont know exactly that i had carb problems... If looking at the bike head on going left to right the 2nd pipe had "blueing" lower than the rest, all other pipes were at the exact same point in discoloration. I was told that wa snormal and that it wouldnt get any better on a 27 year old bike. Would you agree?

Secondly i am not sure what that little adjustment knob is...

[chef1366]

Check the petcock

[salty_monk]

Screw under the carb is likely the stop for the throttle... use it for adjusting the idle.

Stumbling when hot like that could also mean that your pilots are too rich. Try turning the air screws on the top of the carbs in half a turn & try again. If the idle now "hangs" (is reluctant to go back to a 1000) then it's now gone lean so possibly not that but it's an easy one to try. Really you should do "best RPM" method to adjust these, you can try that too but this is worth a first shot in my opinion.

Dan

[tsunamimike]

i will check those out tonight, however do you think I should have the cabs synched instead of monkeying around?

Also something i neglected to mention is that when i tried starting it <cold> i pulled the choke out completely and hit the start button and it just cranked and didnt start. Usually you hit the button and the first time it cranks right over....

Now it takes some real monkeying to turn over.... What do you tink?

[doctorgonzo]

Maybe my ear isn't sensitive enough to hear the change, but I've had a hell of a time with "highest RPM" method. Adjusting the screw on one carb doesn't seem to effect the rpm that much.

[tkent02]

Maybe my ear isn't sensitive enough to hear the change, but I've had a hell of a time with "highest RPM" method. Adjusting the screw on one carb doesn't seem to effect the rpm that much.

Look at the tach.
If one carb isn't changing anything, it has a problem, or it's not synched up correctly with the rest of them.

[Smokinapankake]

My GPz did the same thing - turned out it was starving itself of fuel; the vent on the tank was plugged, creating vacuum in the tank, thus, no fuel going into the carbs. Would run long enough to burn all the fuel in the bowls, then die off.
Check to see you get correct fuel flow by draining all the gas out of the tank, through the petcock, set on prime.

[salty_monk]

If you're going to get them synched or do it yourself you may as well pull them apart & clean & replace the O rings....

I was just suggesting a possible no cost solution that will take you about 5 mins.

Dan

[Dave8338]

Valves?

How many miles are on the bike? Have you or do you know if it has had the valves adjusted? You may be trying to get a bike set up to run, with the valves way out of spec and if that is the case, you'll die trying. Just a thought...

[MelodicMetalGod]

Idles and rides great for a while then starts stalling at stop lights after 20 min.

The problem is obvious - you're getting too close to stop lights. The solution is to update your riding routes using Mapquest and their "Avoid Stop Lights" routing option.

Best of luck!

[tsunamimike]

when you say valve clearance what are you reffering to exactly?

I do agree with the stop light idea..

[Craiger]

Valves are actuated by the cam. These valves affect intake and exhaust and are associated with the combustion process. Some motors have valves that are adjusted with shims, some with rocker arms. When these adjustments are out of spec, they can affect performance.