Have a 1990 trail boss 250. Recently rebuilt top end. I'm trying to tune the carb now to get it to idle and run properly. First off it requires being pulled over about 7 times with the choke on full and the throttle wide open when it's cold. Then when it's running it will idle fine but I just reved it a bit and the rpm went up but didn't come back down. The throttle body went back down but the rpm didn't. I have tried messing with the air screw and idle screw but just can't seem to get it to run properly. When I did the rebuild the carb came off to be cleaned. I notice it was in bad shape so I replaced it with a 88 carb from a cycle salvage. I am using the original throttle, and I put a new stock main jet and pilot jet. I also swapped out the needle jet for the stock one too. Am I missing something? Cause its becoming very frustrating. About to set this thing on fire and call it a day... Any advise would be greatly appreciated.