Erratic Idle Speed, Surging Idle

[donner7]

I have an 89 GS500 that we use as a track bike. I was getting the bike ready for a track day, and noticed that htere was a problem with the idle. When the bike is not fully warmed up, when you rev the engine, the idle speed goes back to normal. When the engine is fully warmed up, the idle will vary between 2,000 and 4,000 rpm. Compression is 130 psi both cylinders. Cable routing has been checked, and there is nothing being pinched.

Anybody have a suggestion on where I should start looking for a problem?

Thank you for your help.

[jestercinti]

http://gstwins.com/gsboard/index.php?topic=41199.0

Had the same on my '09. Above post is a good start.