With the right mods your 400 Scrambler can hold its own with any thing out there.
My last 400 would run neck and neck with the 660 Raptors.It just had a HSP speed kit.(I dont recomend tha kit)but it was on my 400 when I got it.

 

Now thats more like what i wanted to hear. Another question when you get a bigbore kit it always says to get a gridle kit for your engine so you dont blow it up with all the new power what is a gridle kit? what would a .02 oversized piston do if any?but it is a wiesco
ftwflh how come you got rid of the 2 stroke and went with the 500 ?

 

First off any time you bump up the compresion or port a 400 you need the girdle kit to keep from busting the cylinder.The girdle is a sandwich like that keeps the cylinder from tweeking.A .020 over piston wont hurt anything.Now port it and mill the head and you need to renforce it.
The reason I dont have the 400 is I got it for my wife and me to play with and it was more than she could handle.Even after a detuned clutch and a Dynoport pipe(still had the power of the HSP)
I ride a 500 because I am a trail rider that needs torque more than hp.I love my 500 it does everything I need.
The 400s are great fun but can be a handfull on tight tech trails.Actually I like the 250 Trailblazers as much as the 400s.Just as fun and can be made to have decent power with no waterpump or counterbalance to worry with.

 

Most guys dont have a clue on the potential of the 400. With some slight mods these can hang really well with teh bigger quads. Just doing a good port job, pipe and clutch work really wakes the 400 up. HPD racemod or AAEN stage 4 kit will beat any stock quad you put against it. Race lighten the flywheel and eliminate the starter. Put a 38mm flat slide carb. This will be super quick. You can get 90+hp from these motors. I think porting, pipe, carb, clutching and trail lighten the flywheel will take a pred.

 

It takes a lot of money to get the scram up to 90+hp. I hade a scrambler with a hpd top end pipe, hpd agressive clutching, k & n air filter, bored .040 over and i raced a predator, it definatly won but it wasnt like he walked away with it either