I have just bought my 2004 Suzuki GS500. When I bought it, i couldn't ride it, as i don't have a licence yet. The previous owner said that the bike will idle high when it gets hot. After he rode it, to deliver it, RPM sat at 4k. I have done a bit of snooping around the internet as well as the forum, and I have read it could be a few different reasons for this to be happening.
1. Valve Clearences could be wrong, I have no idea when it was done last, and do plan on getting this done very soon, the thing that worries me, will this hurt the bike to ride in the meantime ?
2. Carb boots could be cracked/perished. I believe to test, the bike needs to be warm/hot and spray with WD40, and if the revs drop briefly, there is a leak and they need to be changed/fixed.
3. Cables could be to tight, and are slightly leaving the butterflies open, making it rev.
4. Idle could simply need adjusting.
Is there anything else i should be checking? Any help would be greatly appreciated.
You're on the right path.
1) Definitely check the valves first. Even if they are in spec, you'll at least know it, and it eliminates future headaches.
2) Could be the intake boots, or the orings inside. If you think the boots are bad, replace the orings too!
3) Doubt it's from the cables. Next time the idle starts to go up, loosen up the cable near the throttle grip (there should actually be a little play at the grip anyway).
4) "Probably" not the idle adjustment either. Next time the idle goes up, back the idle adjustment down until the engine is around 1200rpm. I'd bet the engine either stalls, or won't start next time the engine cools down.