Is it bad for a 400ex to have the gas pinned as far is it will go? Like in a race, not for a long time, just for a short little race? Is it bad for it?

 

There is a relimmiter so ya cant over rev it but for a few sec's it likely wont kill it!

 

Like trevor said, there is a rev limiter.
I have had mine pinned on the beach for over a mile and no harm done.

 

so it wont hurt it, should a jetted and pipped 400ex beat a kx85?

 

no it wont hurt it and yes u should be able to smoke an 85 i can out run 125's easy so dont worry

 

cause i used to have the kx85 and i sold it to my neighbor and got a 2003 400ex, i got lrd pipe,jet kit, nerfs,grips and new bars, and i have never topped it out fully so i think i can beat him, he pulls away on top speed

 

bump

 

outrun 125's my friends kx125 takes out raptors