Hi. I was wondering if anyone has a 390cc kit on there 250x and what kind of power gains you get out of it? Is it worth the $750? Will it be able to keep up with 400EX's? Thanks.

 

If you can get that for $750 redy to go you found a killer deal. That should get 35 plus HP. Stock is only around 15, so a good gain.

 

Where did you find that 390cc kit for the 250x? I'm starting my rebuild right now and I can't find it.

 

250cc to a 390cc. Is the 250x engine built that well? I mean, wouldn't that be hell for the OEM parts you leave on the engine?

 

thats bs the bottom end wouldnt hold up!!! read my modds and u will see what it takes for a 250x to run with the 400's i readdy dont thing it can be bored out that big b/c the place wher i sent my engine said the highest i could go in the cylinder period was lik 84mm over with a 13;1 compression so thats what i think

 

I assume its a stroker,bore kit. I had the powroll 352 and it made great power but you need a lot more than just the kit to get it. Dump another $1000 in for pipe,36mm carb,cams,springs,oversize valves,porting,ect and it will be more power than stock 400exs but whats the point. Then you will need to do chassis work on the 300ex to handle the power . I loved the 352 kit more than the 406 but be darn sure you get a heavy duty rod. The stock rods snap like preztels. And dont use an rev box. When all is said and done it would be cheaper to buy a used 400ex than what it would take to beat one.

 

hey 1998 fast 250x, what did that put your displacement at? Did you have a stroker?

 

Ive seen that in a ad in Dritwheels. I heard you can do it but you have to dump a lot of money into the quad so it could take the power and its really not worth it. I think you would be better off with a 400ex or swaping the 250 motor for a 350x like I did.

 

what is the 250xs stock stroke?

 

well i didnt go with the stroker kit it tears up the engines really fast and i really dont know what ya mean with dissplacement!! i have 111/2:1 compression and i didnt advance my timing if thats what ya mean... but explain and i will tell