So close and yet so far away...gas leak & fluctuating idle

[Hobbes306]

Hi guys,

Been restoring a 1980 GS450L on and off for the past two years. I got it running decently, but an unsteady idle, backfiring, etc told me I had some leakage somewhere. So I got the carbs cleaned by a mechanic friend and had all the o-rings replaced, got new intake boots and intake o-rings, and replaced the fuel and vacuum lines.

Put the bike back together and she ran like an absolute dream. Fired right up, excellent throttle response, the works. Only odd thing was that after a quick jog around the neighborhood, I noticed my idle was sitting at 4000. I attributed it to still needing to be tuned up and such, and parked it in my garage overnight and the next day purchased some paint for my final touch-ups. Go into the garage that night and am greeted by the thick smell of gas and the sight of a big puddle underneath the bike. Great...

Upon closer inspection, gas is dripping mainly out of the hose coming out of the bottom of the airbox, as well as the left boot between the airbox and the carb (bike tilts to the left, and I guess now I know that clamp needs to be replaced). Oil didn't smell like gas though. Fired her up again and she still ran great, but I still had the idle increase up to 4000, and sure enough a pool of gas collected under the bike yet again.

Does anyone have any idea what is going on here? I know the petcock works, as it wasn't leaking any fuel before I replaced the things I mentioned before. If the bike is running too rich, could it flood the engine like this? What is going on with my idle? Any help is appreciated!!!

[tom203]

I doubt your "petcock works" correctly or you don't understand its positions. Do you still have a petcock with lever??? In "ON" or "RES" spot no gas should flow if bike ain't running- why don't you check by disconnecting gas line and see what happens -leave overnight if need be.

Your float needle seats might be leaking also, but first check petcock. Watch out for rising oil level in crankcase, in case gas is getting there.

High idle after warm up- just try lowering idle stop screw

[Hobbes306]

Before I rebuilt the carbs, it never leaked gas or flooded the engine with the petcock in the ON position. Seemed strange to me for the petcock to suddenly be leaking now. For the idle, I did lower the idle stop screw, but the next night it did the same thing, jumped up to 4000 after a little riding . Am I supposed to have to adjust the screw that much every time I ride?

[Agemax]

it wont matter if the bike is running rich or not, it wont cause the fuel to leak when the engine is not running.
for the airbox to fill with gas the petcock has to be flowing fuel with the engine off so you must have a faulty petcock or you are leaving it on prime, either way the float valves are passing fuel.
the high idle issue is more than likely an air leak. i guess you need to go over all the work that your mechanic has supposedly done and check it all again

[tom203]

Your petcock is likely 33 years old- like me, it can fail at any time without warning. Don't wonder about it, just check it for proper operation.

[Hobbes306]

Thanks for the info guys, I'll bite the bullet and examine that petcock. Been replacing so many things, thought I could get away with keeping at least something original...

There's been a recent development. The bike is currently in a friend's garage, and he told me he took the bike out for a ride and when he got back he put it on it's center stand (instead of the side stand as before), and that it has yet to leak any gas. Is such a thing even possible???

[Steve]

Is such a thing even possible???

Evidently, ... well, ... yeah.

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