I cant sell my fourwheeler cause i owe more than its worth, so i wanted to try and just upgrade the motor and tranny and what not. i have a 02 400ex, is there any bigger motor that is easy to put on it? or does anyone else have any recomendations on how to get outa the hole im in with this thing.

 

Buy a big bore kit for it, pipe and a set of cams. Get that set up right and it will run. The 400s used to rule the dunes untill the 450s and 700s they can be made real fast.

 

That engine is dead solid reliable, until you start messing with it internally!

If you haven't done the usual mods like opening up the air intake, an aftermarket air filter, and a header and muffler....and of course a rejet, then do those and just be happy you have something to ride!!!

Upgrade the tranny??? Maybe you mean trying some different sprockets to change the gearing???