I just purchased an 86 atv 250r and i am putting the motor into my 400ex frame.The motor needs a rebuild and i was wondering what option would be better for mx (250,265,310).you ask,why not just buy a fourtrax 250r? Well the fourtrax was never made available in Australia,Unluckily for us.We only run an open class so cc's don't matter.I've also seen that the bigbores are sometimes not as quick around the track as the 250r.I need some help with my decision and any info would be appreciated. Thanks......oz_400ex

I don't know how much of a help this will be, but one of the magazines did a comparison of equally equiped 250, 330, and a 4-stroke. They said that the 250 got the best lap times, but wore you out the most, the 4-stroke got the worst times (I think), but wasn't nearly as tiring as the others. With the 330 being somewhere between. I hope somebody with more knowledge then me replies.

this is my .02cents if you run only the open class bigger is better go for the big bore but if dont want to split the cases go for the 265 kit i run a 265 kit in one of mine and in the dunes i get almost all the whole shots when we drag but then lose the race against banshees and big bore Rs my other R has a bigbore 330kit and it runs on race gas and for the upkeep and expense the 265 keeps going and going so i hope this can help by the way you should check the bottom end if you dont know the history on the atc you would hate to build even a 265 and have the bottom end go south on you

ride hard ride often

ESR(www.esr250.com) makes a 310 kit for R and it's simply bolt on. You don't have to machine the cases, just bolt up the new cylinder and head. I've heard it produces great power, and am considering gettin one myself for my R when the cash comes in. I believe with match porting, and cast iron, it's $795. That includes cylinder, with match porting, two piece head withe one dome(use choose size), and all the necessary nuts i believe.

if you have alot to spend, look at a PC 2000: power valve cylinder from DuncanRacing. the kit is 2595.00 for a 250/275cc setup. if i had the money i'd have one by now, i havent heard anything bad about it except for the price. best luck to ya

350 power valve! thats what i would get. or a 440 polonda lol. neither of those might not be the best for racing though.

If I were you I would see if anyone makes a 265cc powervalve kit.


1986 honda trx250r-esr chrome pipe and silencer, ac skid plate, renthal bars,douglas rims, razr rear tires, ac front bumper with mud screen

I have a Pro X 350 powervalve motor in my '88 250r and it has very manageable power. You can lug it through the tight corners much easier than a non powervalve motor. I have owned several 295's and I prefer the 350 powervalve by far. Easier to control and much faster. By the way it's for sale if anyone is interested.

Bigger piston diamater doesn't always mean a faster speed. Many 416EX's will outrun 440's with a milder cam. Back to the question though.

250Rampage was talking about Kory Ellis' quads. He has 3 MX bikes. One is an LRD265, the other is an LRD330, and the last is a YZ426R. Dirt Wheels reported that they could crank out better lap times on the 265 on tigther MX tracks, because the 265 pulled harder than the 330. This is true. I ride with a 265R and a 330R(sometimes), and I feel I can go smoother on the 265. Now every experienced racer knows that smoothness equals speed. Eddie Sanders Racing(ESR) is building one helluva reputation of making solid motors. I dont think you could go wrong with any of their kits, but they're on the expensive side.

Really what I'm trying to say is, don't follow the misconception that bigger is always better. I believe the reason that the 330R isn't as good on an MX track is because it has a really high top speed, and that's where that motor kit shines. A 265R is really all I would ever want for the tracks that I race at. Hope I helped,

Thanks for the info,the tracks here are fairly tight so i think i'll go with a 265 kit.I was thinking of either LRD or ESR what do you think ...oz_400ex