Help!! I bought a '98YZ400 and it starts fine but won't idle after it's warm and the choke is off. The bike was sitting since May so I replaced the gas and cleaned the pilot & main jet, and still no luck. It also pops alot when I have to keep it running with the throttle. I took it to a local shop and they cleaned out the carb and a new plug and it still won't idle ! They suggested a whole new top-end job !!! The guy I bought it from says it was running perfect when he last rode it and that there's no way it needs a new top-end. (He seems pretty honest, an old Dist. 37 guy) Anybody have any suggestions out there ?? I'm getting desperate !!