2nd owners of a pretty clean 2004 CRF150F bought last year for my 15 yr old son. Runs pretty good but little problem with idling high after it gets warmed up. Noticed this the one time I rode it so dont know how long its been going on. I changed the spark plug, air filter and checked valve gaps(are within specs). Also, I should mention that when first starting the bike after being cold overnight it, I have to adjust the choke lever in order for it to run until it gets warmed up. then can take choke completely off. Does this sound like I should adjust the idle screw when its warmed up or will it require cleaning the carburetor (I do run it with stabil in the gas).