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Hello,

I have a 1995 XR250R, the cam chain broke and a few other things...anyway the mechanic suggested getting a high compression piston, and said I would notice a considerable power difference. I went ahead a told him to get the high compression piston. the mechanic is having trouble ording the right valves, so with this time I have been thinking what will the perfomance difference be like? so if you guys could me out, High compression piston vs normal, i would really appreciate it.

Thanks

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Typically you wouldn't bump up the compression unless you're running bigger cams or higher octane fuel. It's also nice to have a safety margin on an air cooled engine because hotter weather could cause detonation.

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As long as you don't go too crazy with it. Keep it real mild.Some people modify the crap out of xr's and to me it sort of takes away from the point of the bike. They were great how they were(uncorked of course)for what they were intended for. 

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I think standard they are 10.2:1, I wonder how much more you would get out of it going to 10.5:1 ?

Also I would only change pistons if I was going to bore it as the bore needs to be matched to the piston, chances of your high comp piston fitting your existing bore perfectly are pretty remote bearing in mind there can only be 2 to 4 thou difference from piston diameter to bore diameter.

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You could always punch it out to a 280cc, run a Hotcam, get some head work done etc,

I have never ridden one but apparently they are a beast.

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