cp high compression piston?

5 replies to this topic
  • probikerguy2

Posted January 12, 2007 - 07:50 PM


i have a 2000 426 and was curious about the cp high compression piston, how much do you gain from it? does the higher compression require race fuel only? is it worth the trouble?

  • Big Zero

Posted January 12, 2007 - 09:29 PM


I receintly put a CP in my 450 and gained around 3hp., And 3 ft. lbs. of torque. Your results may vary depending on cams, exhaust, and any headwork that may have been done. A well respected long time Yamaha guy highly recommends the CP picton over all others.


Paul G


Posted January 12, 2007 - 09:30 PM


If you go up one degree, say from 13:1 to 14:1 then you will be fine, and there will be no need to run race fuel, although if you do use higher octane you may see even more of a benefit. The gain is in the bottom end, you will get more torque from a hi-comp piston.

Go with a forged piston, not cast, and it will be very reliable.

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  • 642MX

Posted January 13, 2007 - 07:24 AM


I use a Wiseco 13.5:1 piston and besides a little more piston noise, its well worth the money. I do use race fuel, only because it will ping on heavy loads when its hot. I noticed a big gain from bottom to mid, but nothing more on top. While I'm sure the CP is a good piston, I'd recommend a Wiseco from personal experience.

  • j753301

Posted January 13, 2007 - 03:43 PM


just my opinion but i always loved je pistons,great quality and fit.

  • Big Zero

Posted January 13, 2007 - 09:05 PM


From what my guy has said (my guy being the R and D guy for Hot Cams for several Years) the JE Piston has the worng shaped dome which disrupts the flow of intake and exhaust gasses.

There are so many differing opinions reagrding what works and what doesn't, that I don't know what to believe anymore. MY guys says the JE is junk.

The higher compression will help the Hp as well as the torque. Race fuel may be recommended, but not required. I have run both, and have felt little difference.


paul G

The higher compression will help HP as well as torque.

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