GS500 engine idle problem . . .

[PPS]

I'm new to the forum, and also to motorcycle mechanics . . . so I'm hoping for some advice.  I'm a decent parts replacer, but not a mechanic! 

I've been rebuilding a 1990 GS500 that I rescued from my nephew who left it in the rain for YEARS.  Finally got it cleaned up, replaced a bunch of (exterior) parts, and actually got it running (new carb jets, etc.).  Problem is now that when I start it, it idles for about a minute, and then revs to 4-5k rpm and wants to stay there.  Adjusting the choke doesn't seem to help it.  I'm pretty sure the throttle cable is set right. 

Any thoughts on where I can look from here?  I'm sure I'll need to tear into the engine at some point and clean it up really well, but would like to postpone that if I can just get it running and operable right now.

Thanks in advance, the forum has been great for me just reading and learning!

[BaltimoreGS]

Welcome to the forum, try starting here:  http://gstwins.com/gsboard/index.php?topic=41199.0

You can also search the term "hanging idle."  Might be as simple as an air intake leak or misadjusted pilot screws.

-Jessie

[bombsquad83]

You mentioned the throttle cable, but not the idle screw.  Does adjusting the idle screw (the big one in the middle that sets the base for the throttle opening) once the bike is warm help bring down the idle?

[PPS]

Thanks for the link to Buddha's list of things . . . that's very helpful.  And, I'll also check the idle screw.  I thought that the big screw in the middle was for adjusting the sync on the carbs . . . I'm presuming from your post that I'm wrong on that, so I'll look into it.  I did drill out the plugs for the air/fuel mixture screws, but haven't adjusted them further at all (just removed the caps).

I'll report back, especially if I still can't fix this.

Many thanks.

[PPS]

Uh, ignore that comment about about the carb sync screw . . . I was thinking about something else.  But, you're right . . . I hadn't checked the idle at warmed up temperature.  I hope it's that easy.  Although I'm sure there's a small leak in the exhaust pipe.  It was rusted out on the bottom leaving about a 1" hole.  I tried to weld it up, but evidently I still have a small leak (I can hear it with the bike running).

SO, I'll get those things fixed and hopefully we'll be good to go.

Thanks again.

[bombsquad83]

You might have disturbed those mixture screws when you drilled out the plugs as well.  You might want to bottom them out and go back out 2.5 to 3 turns.

[PPS]

Good point.  Thanks for the suggestion.