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high comp piston ?'s

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so when going to a high comp piston i heard that it brings on more bottom end and that stock will keep the stock curve.

is this true?

is the high comp bottom end at the expense of any top end

does it change the whole curve or just add to the bottom??

thanks:thumbsup: :)

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You just asked a loaded question, but in general more compression will increase power throughout the rpms range if jetting, camshaft profile and exhaust are relevant.

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It adds to the whole curve, not just bottom end. Sometimes people notice it mostly at the bottom end because relatively speaking (i.e in percentages) you've probably made the most gain there.

But due to the dynamics of exhaust, cam, head, flow etc you might end up finding it more noticeable somewhere else in the curve such as the midrange.

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Just my opinion but going too high on the compression defeats the purpose of going that direction to gain more power. I personally wont go any higher than 14:1. I know too many people that go up to almost 15:1 and have problems such as hard starting and loosing some overrev. Just my .02 :)

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i wasnt considering going higher than 13.5-1

will i still notice performance gains with this on my wr250f

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Yes you will. I install the 08 piston on all of the 06/07 250F's that I do top ends on.

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On most 250F's it seems that 13.5:1 is about the best comprression ratio. Much higher than that and you start seeing a decrease in power across the RPM range on most 250F's, unless substantial engine modifications are done.

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sorry to keep you going KJ790 you have been a great help but what would the substantial mods be

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sorry to keep you going KJ790 you have been a great help but what would the substantial mods be

Cams, porting, exhaust, valve size, and ignition timing all work together with compression ratio. If you want to run a compression ratio outside of the optimal range for your engine design, you need to change some or all of the other aspects of the engine to make it perform right.

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