13.75:1 CP piston

12 replies to this topic
  • gtxkid

Posted April 04, 2008 - 04:39 PM


Main question i have is:
What do you guys think of the new 13.75:1 piston.

Second question is:
Should i do anything else while i have it apart.
I am going to have it installed after the race this weekend.
2008 YZ450F
Will put a new cam chain with it or not, Bike only has 14 hours on it.
I am after low end and midrange.
Pro Rekluse is best thing i have ever done.
I have a stock pipe and not looking for a ton of power on top.

  • Qwik Gixxer

Posted April 04, 2008 - 04:54 PM


Race gas only with that piston. Higher compression means faster throttle response.I would also reccomend a pipe and jet kit.

  • gtxkid

Posted April 04, 2008 - 05:02 PM


I agree a pipe
I thing the guys are saying July for the new one's

  • Bigcr

Posted April 04, 2008 - 09:03 PM


Go up one tooth on the rear sprocket.

  • grayracer513

Posted April 04, 2008 - 10:01 PM


If it were me, I would not do the piston before I tried the bike with a different exhaust. You are looking for more low and mid range, and even a used '06 pipe slipped onto your header would give you 5 or more extra horsepower at 5000 RPM.

13.75:1 is a very high compression ratio, and you would get more low/mid power from it. However, you will not get the kind of gain you would get from opening the exhaust system up in the particular case of an '08, and the increase in compression will more than likely carry the on-going penalty of having to run race gas in it.


Posted April 05, 2008 - 08:48 AM


I ran a 14:1 compression custom venom/kbr race CP piston in my YFZ and even though it is in a quad motor it should be a very similar situation. It gave me a ton more bottom and mid range torque, but because of my other mods gave me a bunch of top end.

I will not run any brand of piston in my stuff other than CP though. I firmly believe that they are the best pistons made for this type of application.

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  • gtxkid

Posted April 05, 2008 - 07:36 PM


I practiced today.
Yes i already had them put on the parts truck for tomarow a 50 tooth sprocket.:confused:
I broke my chain in a race last week so i put the order in for a new sprocket also.
having a hard time on the pipe, want to wait a little more to see what new stuff come's out before i decide.:thumbsup:
I need the zip tye mod
I love my pro rekluse.:thumbsup:

  • racegmc

Posted April 06, 2008 - 05:50 PM


I have an 06 450f and have at least 150hrs on it. Never have had to replace anything internally. Starts up everytime with no problems. So my question to you is, why would you open it up if you have not tried an exhaust system, filter or any other bolt on products yet. These are awesome bikes and are very reliable. I would do that first before spending money on internal parts that are still good.

  • Aka.Goose

Posted April 06, 2008 - 06:13 PM


why would you open it up if you have not tried an exhaust system, filter or any other bolt on products yet?

I agree...
new pipe...
50T sprocket...
Zip Ty carb mod...
replace the piston later on...

Just my opinion though...

  • gtxkid

Posted April 06, 2008 - 08:44 PM


I agree with you guys and have put a lot of thought into it.
I have always wanted to try and go this direction.
I even talk to a lot of people at the track and have mixed opinions.
I do not mind running race fuel, i mix 50/50 anyway.
Production bike is made to run on 91 octane.
The 50 tooth sprocket worked out great.
The rekluse worked out great.
I have a suspention guy that goes to the races and let him do the settings when i think something neds it, this brought me from last to sometimes first over the last two years.
Now the other man i am working with is a very well known Pro and has been one for years.
He is very good and honest person.
If i do not like it i will take it out.
Few other guys with them realy like it.
I will wait till June or July for the new pipes to come out then i will get a nice one.
I am going to do the zip tye mod also.

  • gtxkid

Posted April 14, 2008 - 06:19 PM


I raced three class's yesterday and love the piston.
Worked out great.
Now i will wait for a pipe, hopefully something cool.
Probly something practal like the Dr D that you can lower the raidators on.
Have some friends that realy like lowering the center of gravity, they tell me it works good.
I am in no hurry, there is a lot of life left.
Some people have different opinion on race fuel.
I do not mind running it because i feel it is just part of it.
Love the Rekluse.

  • ProjectDIRT

Posted April 14, 2008 - 09:14 PM


i just got the race piston and some hot cams will let you guys know how it is.

  • gtxkid

Posted April 15, 2008 - 08:03 PM


Cams-----I didn't think of that.
Interesting to see how it works for you.

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