TC did a couple of conversions of the 250X motor by marrying a 350X cylinder to the 250X motor, (requires serious case buttressing and redrilling) He built one for Travis Spader that was incredible and still smokes a lot of the latest stuff out there. But mounting a 350X motor is cheaper and easier......and more durable.

 

it is possible but expect to be changing the piston and cam with all of the bolt-ons at the very minimum.

 

Manual, there are 250X's and 300ex's that may beat stock and slightly modified 400 ex's as well as some others, but not with a filter, pipe and jetting.

I have run two heavily modded 250X/350x conversions which was the four stroke of choice on the before 1999 and the 400 ex came out, and these were competitive with anything out there......not necessarily faster than all but faster than many 440 ex's, many modded Raptor's, quite a few banshees, lot's of r's from 265's to 330's,(displacement is NOT the whole story) and several modified Cannondales when racing flat track - which may give you a better pure horsepower comparison for pure speed and acceleration than any other type of racing short of drag. To get up there into the mid forties(hp) at the rear wheels takes a lot of doing and obviously into the 50's takes even more. That's what a lot of these bikes run at.

So when you start with 17 hp in a 300ex, you are talking almost tripling the power to get competitive with heavily modded versions of the bikes you want to beat.........possible but very expensive...transplants are cheaper.

 

dude I didn't know that you could mod a 300ex to beat banshee's. that would take a ton of money. You could pick up a good used shee for the price of modding a 300ex that much.

 

I agree. and if you ever got that much power out of that motor it would last about one good race and you would have to start over.

 

a video is on www.exriders.com the 300ex takes off fast... supprised me

 

I have that one on my hard drive[img]i/expressions/face-icon-small-smile.gif[/img]

That is fast. Out of nowhere though I hear the banshee catching up to it. Anyways, I think I should drop a snowmobile engine into my ATV...

 

Roosthrower - it was actually a 250x frame (same thing as 300 ex frame) on flat track we beat almost all the Banshees - torque is an issue pulling out of the corners. Not Sue Parkers though......an East Coast creation. My second flat tracker with a 423 cc /350X - not stroked, was pulling close to 50 hp at the rear wheels. It beat a lot of Cannondales (piston, mapping etc.) most 440ex's although not all, most 250r's even the 330's etc. again on oval track the torque pull coming out of the corner has a lot to do with success. Beat every Raptor we raced with that bike - except one.

Have one of those motors still left - special intake setup helped a lot.

 

i have seen 330 just yard a 400ex

 

hey crobiker how long do u expect your 300ex to last trust me if u do get all that stuff in it your 300ex wont last long so when your moter gives your freind will will have a faster bike