02 mountain cat runs like crap

Could be either the air or water temp sensor.

900 engine dies

Mine does a similar thing. Just started happening all of a sudden about 3 rides ago. When you start it from hot you have to keep the throttle on else the rpms will slowly drop and drop and drop until it eventually dies.

From cold with the choke on its fine, but the same thing happens when it warms up and I take the choke off.

Ive been meaning to check this air temp sensor. Anyone know where its located and if its an easy test/fix/replace?

Air temp is usually in the air box. If the sensor over-reacts it can starve your engine on a hot start. Both sensors feed info to the ecu. Those sensors along with the barimetric pressure sensor built into the ecu regulate the injector duration. Both sensors can be checked with an ohm meter. I don't know how much the numbers have changed over the years, but the testing method is easy. Put the water temp sensor in a cup of water along with a prob thermomitor. Check the ohms from the body to the wire conection. ohms will keep rasing the warmer the water, 50*F water will be 3.750 ohms, 100*F water will be 1.214. Air temp sonsors will require an accurate air temp thermomitor. 50*F resistance is 20,100 at 82*F resistance is 8,540. A dealer will have complete charts for your model. These were taken from a 1997 chart, pre 97 had a battery operated efi and very different factors.