1999 Honda 400ex. no balls!?

I've cleaned the carb,air filter and this thing still is screwed up. It starts,runs and idles fine, when you give it gas it just dosent want to go(fast) I haven't changed the plug yet, never seen this happen due to a bad plug. I guess now I'm leaning twords electrical? Any ideas in the right direction are greatly appreciated.

What mods are done to the quad? IS your jetting correct? How many hours does the motor have; Valves?

Pipe, jets,exhaust. We were out riding was running fine then on the next ride it does this. Not many hours on the motor. Can't figure out what the hell is going on! Could the valves case a problem like this? All the sudden? It was a matter of about 20 mins!

When i got mine it had almost the same problem, i just re-jetted it and it runs great now

* Moved thread to Honda forum and added year and make to thread title.

check your intake boot for dry rot cracks and pin holes will cause this and check choke pistion check and make sure the choke is not closing when reve the motor.