i want it to be faster then 450s with out like boring the 400ex engine so i was wondering if anyone had any suggestions on what other engine to put in it

I still want it to be a 4-stroke
i was thinking like a yzf426 dirtbike engine or a crf450 engine Probaby which ever one i can find for cheap so if u now of any for cheap please let me no because all my friends are smoking me now

 

cbr600 or an r6

 

CR250 2-stroke

 

yeah the CR is a bad @ss engine...but it is going to vibrate the hell out of you in a quad since it isnt counter balanced. they got years of technology on the TRX design and make allot more power (was typical with dirtbikes to get the good stuff first but the tide seems to have turned in favor of atvs getting newer stuff).

doesnt service honda still sell a cr250r powered 400ex bike for like 8K? too much for what it is, imo. i just think by the time you find one, the combined price is going to be what you could go buy a 450 or raptor 700R for! i have seen some mean 440s beat the 450s. sounds impossible but true. id do that before the headache of swapping engines and fabricating stuff to work...unless you are or know someone who has the time and can do it right. you dont want any cheapo parts or crappy fab job here; your life could depend on it.