I just rebuilt my sons Honda TRX 90. I had it bored out ten thousandths and the valves lapped. I put it all back together and adjusted the valves with the motor cold of course.
I took the carb. apart and cleaned it all up. Its not completely broke in yet, but when I start it up it I can't get it to idle very good. I've jacked around with the pilot screw and the idle speed adjustment and it doesn't seem quite right. When you punch the throttle it completely bogs down and wants to die. If you gradually increase the throttle it revs up fine. If you jab it about 1/4 throttle then the motors revs up high and stays there for about 5 seconds before returning to normal idle. I've looked all over and can't find no air leaks. Since I adjusted the valves when it was about 50 degrees in the garage could that have anything to do with it. The manual called for the motor to be warmed up when adjusting the valves. Is it possible now their to tight when motors gets hot? If so has anyone ever adjusted their valves to tight and if so what happened? If anyone has any ideas I'd appreciate the help. Thanks DennisC

 

If the valves are too tight, youll lose some compression, and it usually shows up in hard starting.
Look for vacumn leaks and loose mounting hardware, around the carb and intake.
You have the air box and lid on?

 

This is typical of an air leak in the intake track. Spray some wd-40 around the intake and see what you come up with.

 

Yes the air box lid is on tight. I'll try tomorrow the WD-40 trick on it. Thanks DennisC