205x u understand that the stroke is how far the piston moves up and down?
That might help to understand

Yes i do understand that, thanks for checking though.

so no we got straight that the 300EX head Will fit on my 250X case, but to get it up to a 330, you need to sawp the rod and crankshaft...which means more than likely, the case will need machine work??

how reliable of a setup would this be?

A 330EX doesn't have any stroke work at all. Instead of the stock 74mm piston, you press out the old sleeve and install a new sleeve with a 80mm piston(80mm piston equals 329cc). Some people then install a 2mm stroker crank and pump up the displacement to 352cc. This motor is very powerful. 80mm piston, new sleeve and piston hardware cost about $300 bucks. Plus there is some labor cost involved with pressing the cylinder and boring the topend.

If you have any questions, let me know.

IF you put a stock 300ex head on a 250X, put in t 300ex crank and rod..you know what you'd have a 282cc 250X motor with 300ex parts!

how would this make it a 330? If it were that easy i would of bought a 250X bottom end and saved myself a 1,000!

A 330 has an 80mm piston. stock is 74 i believe, thats a 6mm over bore.

hey Cstark we said the same thing at the same time LOL

yes i do realize that'd i have a 282cc motor, but what i was wondering was if there would be any advantage to having the 282cc bored out and going with the 330cc kit, or just staying with the 282cc?

just the 282cc head with minor mods like high compression piston, and the rod and crankshaft...which would be required to get the full 282 cc out of the motor...how reliable would this be?

and how reliable would it be with the 330 kit?

Aaron, great minds think alike........[img]i/expressions/face-icon-small-wink.gif[/img]!


Last season I raced a fully-built 282cc motor. This year I race a fully-built 330cc motor with bigger carb. Huge difference. They always say, "there is no replacement for displacement." That saying couldn't be more true. But with every advantage, there is always a disadvantage. My race motor needs a new topend every year, valve adjustment after every ride, and new oil and filter after every 5 hours of use. This gets very spendy. You have to decide if all of the extra time and money is worth it. Only you can make the call. Race motors run fast, but they never run the same after you crack one open.

Good luck with whatever you decide.

i agree fully with everything chris said

I tuned 282 motor runs good, but a 330 will run circles around it.

The power is amazing. But mateninence is greater. I don't race, just trail ride, so i imagine my top end will last a lot longer. My racing career was cut short by my parents, and lack of funds to support quad parts.

If you just trailrode every day about how often would you have to adjust the valves?

It doesn't matter if it's on a track, down the trail, or in your backyard. If you beat your machine, things are going to break. If you decide to go with a 330 kit, you will need to do more maintanence on your quad. The combination of more heat, more power, and remaining stock components will in time, break down. Like I said before, it's your call.


It's a good idea to check the valves on a regular basis on any 4-stroke.