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2010 piston does fit in 09 250F

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howdy all, i've just got done rebuilding my 09 KX-f 250, i was intersted to see if i could get the '10 piston to fit in an 09 engine, so i did that just, i bought a few extra base gaskets, a 2010 piston, when pulling the bike apart, after removing the head i made up two spaces so i could torque down just the barrel to squash the gasket/s and get an X dimention measurment by placing a strait edge across the top of the barrel, and using feeler gauges to measure the space between the top most point of the piston and the cylinder head (0.95mm), when installing the new piston, i simply added base gasket's until it came to the same measurement (actually ended up woth 1.15mm using 3 base gaskets)

i havn't run the bike yet, but it will definantly be a tentative first few minutes that's for sure, i also found in interesting how light the stock 2010 piston is, the previous owner of my bike had CP custom make a 14.6:1 piston for the bike, worth around $800 aus, while evan though the stock piston is only 13.2:1 (which is still plenty) the entire assembly (piston, pin, rings, clips) is 18 gram's lighter then the CP piston i took out (181 vs 199), and for only $280 AUS.

i'll be test riding the bike in a few hours and will report back how i went.

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👍

howdy all, i've just got done rebuilding my 09 KX-f 250, i was intersted to see if i could get the '10 piston to fit in an 09 engine, so i did that just, i bought a few extra base gaskets, a 2010 piston, when pulling the bike apart, after removing the head i made up two spaces so i could torque down just the barrel to squash the gasket/s and get an X dimention measurment by placing a strait edge across the top of the barrel, and using feeler gauges to measure the space between the top most point of the piston and the cylinder head (0.95mm), when installing the new piston, i simply added base gasket's until it came to the same measurement (actually ended up woth 1.15mm using 3 base gaskets)

i havn't run the bike yet, but it will definantly be a tentative first few minutes that's for sure, i also found in interesting how light the stock 2010 piston is, the previous owner of my bike had CP custom make a 14.6:1 piston for the bike, worth around $800 aus, while evan though the stock piston is only 13.2:1 (which is still plenty) the entire assembly (piston, pin, rings, clips) is 18 gram's lighter then the CP piston i took out (181 vs 199), and for only $280 AUS.

i'll be test riding the bike in a few hours and will report back how i went.

It should work:thumbsup:

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first ride went well, no piston hitting head action, just warmed it up, and went for a 20 minutes ride making sure to keep it in a high gear and heavy throttle to bed the rings in, for some reason it sound's saintnificantly deeper, but quiter then before, and there much more "felt" compression when kicking it over, probably due to the rings on the old piston being knackared, however i did also notice it seems to bog down in the low RPM more then before, despite the riding conditions today being similar to last tiem i rode the bike.

can't wait to get a proper ride in on it, but seems '10 piston in '09 bikes is a goer:thumbsup:

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FYI the 2010 cylinder is .020" taller than the 2009 cylinder. The 2010 piston has the wrist pin moved to compensate. Yes, the 2010 piston will work in the '09 and is very light.

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FYI the 2010 cylinder is .020" taller than the 2009 cylinder. The 2010 piston has the wrist pin moved to compensate. Yes, the 2010 piston will work in the '09 and is very light.

yes i know, which was the point of my experiment since alot of people on here tried to say it wouldn't work, no need to talk to me like i'm an idiot.

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yes i know, which was the point of my experiment since alot of people on here tried to say it wouldn't work, no need to talk to me like i'm an idiot.

Easy there hero. I was simply stating a fact that you never mentioned. I was in no way implying you are an idiot or trying to piss you off. Only adding a little info to the thread you started.

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