psi for 12:1 comp piston

As in cylinder psi?

yes cylinder psi . i am trying to compare stock to what i should have now with a 11;1 PISTON

From what I understand you won't be able to get a comp, reading over 125 because of the auto decompression. I have the 12.1 piston and I have not been able to get a reading higher then 125. As for the stock piston you can get a comp reading because max comp on the stock piston is 75, 77 I belive thats whats on the manual.

Thats strange because last night i got a 141 psi reading w/11:1 je piston> I also did a leakdown to test the rings and i was leaking into the case so I tore it down. This is what prompted the question because I remember reading in anouther discussion that a 11:1 should be around 180-190 psi.

Ok just went over to my bike and did a comp test and it read 163 don't know whats going on here. The only thing I have done from then to now is I took the head of and put new rings. Guess I feel like an as. But still should it be higher. Also just fried my stater relay in the prosess it was going anyways.

THATS A GOOD THING , YOU SHOULD DO A LEEK DOWN TO SEE IF YOU HAVE ANY MORE LEAKING. MY QUAD RAN JUST FINE EVEN WHEN THE VALVES WERE LEEKING, AFTER A VALVE ADJUSTMENT WE THEN HERD THE RINGS LETING AIR BY. TONIGHT I AM INSTALLING A NEW SET OF RINGS ON A FRESHLY HONED CYLINDER I WILL LET YOU KNOW WHAT THE COMP IS THEN. MY TECH SAID THAT 20 PSI MAKES A HUGE DIFF IN YOUR POWER.

Whats a leak down test and hows it done. I did my comp test and let it sit for about 1/2 hour and it did not drop.

a leak down is when you put about 50-60 psi in thought the spark plug hole (special tool for this) and hook it up to a compressor. then you put your ear or a listening device to three differant places ( exhaust,intake and down by the crank access hole where you see the top dead center mark) . mine was leaking in the valves so we adjusted them and it stoped. Then we herd it comming out the crank case hole whitch means that it is going by the cylinder. This test works great for finding out if you are used all the hp possible.

i forgot one thing, you have to hold the crank a top dead center while the test is being done. I kind of takes two people.

Cool, thank on the info will have to do this to make sure my vaules aren't leaking. :thumbsup:

Well this is so cool just checked my comp kit and well I alway wondered what the long metal pipe with an air fitting was for and now I now. But how do I know when I'm at 50 or 60 psi. I have a large compressor can I just plug it in. I don't want to blow something trying to check this.

700rider said:

Well this is so cool just checked my comp kit and well I alway wondered what the long metal pipe with an air fitting was for and now I now. But how do I know when I'm at 50 or 60 psi. I have a large compressor can I just plug it in. I don't want to blow something trying to check this.

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You should be able to adjust the psi out on your compressor to around 50-60 psi.

Thanks, :thumbsup:

let me know how it goes, tonight i am picking mine up and i will let you know what the final comp is after the rings were replaced.