What is the engine idle speed? How do I adjust it?

According to Kawasaki's specifications, the engine should idle at 1300 (+/- 100) rpm. The idle speed can be adjusted by turning the idle adjust knob, which is located on the left side, right under the carburetor:

NOTE: Idle speed should be adjusted when the engine is fully warmed up.

Several of our experienced riders say that the 1300 rpm guideline is used by Kawasaki to help pass EPA regulations and isn't a hard and fast number. Some of them run the idle at 1500-2000 rpm. It depends on what makes your bike happy. Set it where the bike seems to want to stay. It won't hurt anything, as long as you aren't setting it high enough to overheat in traffic.

On the other hand, you don't want to use a high idle to compensate for poor performance in other areas. As long as it will drop to your chosen idle rpm level and stay there, you're fine. If it hangs, or is hunting, you'll need to get that corrected, as that's a symptom of another problem. You may have idle mixture or valve adjustment troubles. Poor idle is a give-away of valves being out of adjustment.