My XJ idles high after it warms up. What's wrong?

[radare]

My XJ idles between 2000 and 3000 rpm after it warms up. What's wrong?

If your Seca II idles well when cold but the idle speed increases when warm, you likely have a clogged or partially clogged pilot or enrichment circuit.

Just behind the carburetor butterfly, in the venturi, are three holes (transition ports) which help with the transition from idle to partial throttle. When the throttle is turned slightly, these holes flow fuel and enrich the mixture to help the bike make the transition and account for the increased airflow.

If your pilot circuits are partially clogged and the bike has trouble idling, the idle speed screw is often adjusted so that these transition ports are partially in use. As the bike warms up and the need for fuel decreases, these transition ports provide too much fuel and the bike's idle increases. Adjusting the throttle will let the bike idle normally until the next cold start, when it idles low.

To fix this, remove the carburetors and clean both the pilot circuit and the enrichment circuit. Both of these are very small and easily clogged if a bike is stored for long periods or if it has a rust/dirty fuel tank.