82 KZ1000J2 - fast idle when warm

Howyadoin,

I finally got my bike running, but the carbs definitely have some issues. First and foremost is when the engine is warm, the idle is much higher than normal, as much as 3K at some times. The idle is OK when the engine is cold. Whacking the throttle open and closed doesn't seem to help.

What's the first thing to check, the carb boots? What's the best way to check, spray a little WD-40 around them and watch the idle?

If that doesn't do anything, what's the next step? Checking vacuum lines?

It should be noted that the carbs aren't quite perfectly synched, I have the vacuum gauges, and intend to do that when I get a temporary fuel tank so I can pull off the regular tank and get to the center adjusting screw.

My brother-in-law did a bunch of tinkering with the carbs as well trying to get rid of a flat spot off idle, so I'll reset the pilot screws and make sure I'm at some kind of baseline.

Is there anything I'm missing beside never having worked on a carburetor I didn't set on fire (never hose down a hot carburetor on a Chevy 2.8 V6 with Gumout spray, trust me)?

Thanks!
-Mark P.
Beverly, MA

P.S., here's the obligatory pic:

I would suspect a vacuum leak. Check your carb intake and exhaust boots. Check the vacuum hoses. Obviously if someone has "tinkered" with the carbs you should go through them and make sure everything is correct. Have you checked your choke to make sure it is working properly? With full choke, the rpms will increase as the engine warms up. Closing the choke should return the engine back to the base idle.

Is the engine running real hot?

Before you go any deeper into this readjust your idle screw. You probably adjusted it when engine was not completely warm. When it warms up totally it´ll rev. If it idles without choke when cold you m ight have misadjusted idle screw. Check also your throttle cable that it´s not sticking or too tight? Do the obvious first and them move on to bigger things.

Air leak usually causes revs to drop down real slow not sticking on 3krpm but this can also happen.