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13:1 high compression piston
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Posted by: Hondarider440ex

I have an 04 yfz450 it is stock and i;m wondering if i put a 13:1 piston in it will it make alot of difference and how much.
I have already bought the piston but have not put it in yet and was wondering how much more horse power it would give and if is gives bottom or top or both thanks.

Posted by: YFZ450 11x

I have a JE 12.5:1 piston and it was a noticable differance all around. How noticable is tough to say becouse I went from a basically stock bike in November to this
http://www.upload-picture.com/images/9Nh30362.jpg
I went w/ the 12.5 becouse 13 and up you have to run race gas which is around 8 bucks a gallon. Right now im runnin 50/50 mix 112/93 octane. Seems to work well

Posted by: 03400EX_Nacs

i went 13:1 and it made a WORLD of difference. i am running race gas but its only $6 a gallon here

let me just say when i am in 3rd gear the quad starts to leave me :O its amazing!!!

Posted by: 440racer66

how about a 11 1 piston how much power gain

Posted by: YFZ450 11x

quote:
Originally posted by 440racer66
how about a 11 1 piston how much power gain

Not to much it comes stockw/ a 11:1

Posted by: 440racer66

oh my bad i meant a 12:1 i must have really been spacin last night thanks for pointin that out

Posted by: YFZ450 11x

We all have those days man

Posted by: kawasaki_ridah

I have a stage 2 cam and 13:1 JE in my R and it's so freaking awesome. love it. go 13:1 you won't regret it.

Posted by: tar

I talked to a guy that had a 13 to 1 and he said he would ride it down the block and it would shoot the head bolts out so he got a 11 to 1

Posted by: 440racer66

hey how long does it take to breack a new piston and sleve in ?

Posted by: 440ex dragger

About an hour with your heat cycles I believe. They say to ride it at 1/4 throttle for a tank of gas, then 1/2, change your oil then its ok to go balls out.

Posted by: EvilJester400EX

I had a 13:1 in one of my YFZ's and liked it. Decided to get more work done and it required me to drop down to a 12:1 piston, though. Overall, it's a bit snappier, but you will gain more with a piston and cams combo rather than just a piston.

Posted by: snox31

quote:
Originally posted by tar
I talked to a guy that had a 13 to 1 and he said he would ride it down the block and it would shoot the head bolts out so he got a 11 to 1

i am sorry but the guy that said that is a dumb a** that is not going to happen.

Posted by: 440racer66

god i cant wait to get mine how much horse power am i gonna gain?

Posted by: mountaineer

quote:
Originally posted by 440racer66
hey how long does it take to breack a new piston and sleve in ?

The rings will seat after about 20 minutes. Do not stay at a steady rpm and stay away from the rev limit. Change your oil and filter. And your set. I replace my rings in my 13 to 1 piston 4 or 5 times a year and they seat well everytime. I would also stay away from synthetic oils on your break in only. They work so well they often do not let the rings seat properly.