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Big Bore or High Coppession Piston

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Hello,

I love my 05 WR 250F, I don't know how many hours I have on it, but I have a little over 2,000 miles, I change my oil every 100 miles and am not beating the snot out of it to bad.

My shop says the engine is looks fine.

Two questions,

1- how many mile before a rebuild?

2 -When I rebuild I want more low end. I am huge for a 250f, 240lbs. I would consider a 290 kit or a High Compression Piston. My shop warned me against the big bore saying they break more and over heat.

Just what does a HCP do for you and can you still run regular gas.

I know that is about 5 questions, any answers are welcome.

Thanks,

OT:ride:

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Depends on how high your going to run your compression. If you go to a much higher compression you will have to run race gas cause of risk of detonating.

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Big Bore! Great low end increase. (Be ready to jet down to the 165-170 range) I have Athena 290 in my '05yz with no problems overheating in 60 hours on the meter.

To get much increase in the high RPM range you will need some increased breathing capacity to feed the larger displacement. I added Hot Cams stage II and couldn't be more pleased. If you really want mostly low end, try a Stage I. Stage I made a tractor out of my '02!

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I agree with Harry. Big bore with matching cylinder is the ticket but a little more money. I have a 276 Ice Cube and stage 2 hot cams and its a very bad boy now. When run with U4 fuel it breathes fire!

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Your dealer is an idiot. Both options are safe and reliable, but the big bore gives you a much larger power gain, especially if you go for the Athena 290, or my personal favorite, the Vertex 298. Call Eric Gorr for more information. :applause:

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Thanks for the replys. Any one know about how many miles a stock motor will go. As I mentioned I have a little over 2,000 miles and no idea what that means as far as hours.

Thanks.

OT:ride:

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Thanks for the replys. Any one know about how many miles a stock motor will go. As I mentioned I have a little over 2,000 miles and no idea what that means as far as hours.

Thanks.

OT:ride:

It kind of depends on how hard you ride it and how much time the engine spends at the rev limiter. I see it's a WR. Have you done all the free mods, and put on an aftermarket exhaust?

I would probably look at doing the top end on it, just because. If you do it before it needs it, you never have to worry about it going BOOM. These things get REALLY expensive to fix if they blow up.

Unless you have recently changed it, it's time for a cam chain, and maybe the intake valves. Hopefully you've been checking the valve clearances regularly.....

If you feel the need for more power, definitely go with the big bore kit. The Athena 290 is quite nice. I've installed a few, and have one sitting on the shelf for my new bike. If you don't feel like doing the big bore, you can safely run a high compression piston. The HC piston will give you more bottom end. A set of Hot Cams will help too, Stage 1's give more bottom end, Stage 2's give more top end. Of course the big bore and hot cams would be the ultimate, but that can get a little spendy.

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I am 240 also,(damb i hate typing that). i did athena 290 and stage 1 hotcams at same time to a yzf and it was a $!!!ton more power on the bottom. that combination is almost to much, even at my(our) weight. I would not go with big bore and stage 1 again, i am looking to get stage 2 cams now so the power is spread out more and "wider".

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