My 400EX had no throttle response a while back. no wheelies, burn outs, acceleration, did only about 25-30 mph. I had a clutch put in same thing, i bored out the piston, new piston, new clutch cable and it worked fine. Now it is doing the same thing. is it the piston again or is the whole thing junk please help me!

 

well the problem is its a honda.

 

It sounds to me like the problem is in the carb. When was the last time you drained and cleaned the float bowl. Also, have you done any recent airbox or exhaust mods? If you have, you need to re-jet.

If you ease into the throttle does it pick up speed? If you pin the throttle does it bog down and want to die? If the answer is yes to either of these, you problem is more than likely some dirt or something got into your gas tank and is clogging your jets.

 

Thanks TRX450Rrider. It was the carb. it is running great now.