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compression test


bunboy1

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hi all,

 

i am doing a complete rebuild. i just stuffed the motor and i am doing the compression test. i have the carbs and pipes off and i am getting 130 psi on the left and 120 in the right. are you suppose to have a spark plug in the hole you are not testing? i have a +4 crank and 21cc cut domes. my squish is .056 and .057. i am in just above sea level and its like 75 degrees in california right now. how much psi does the test hose hold? is this normal? thanks

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leave your carbs on, start your bike and get it nice and warm. kill it and pull the plug, put in the tester and remove the cap from the other side. open the throttle wie open and start kicking until the needle doesnt move. (10-15 kicks) thats your static comp, release pressure and do the other side, should be within 10 lbs

 

a stock bike is around 125-135 psi... port work can drop this a little, also dome size makes a differance. it hard to say if your comp is good. how was it when the motor was fresh? if you started at 180 and now its 130 your over due, but if it started at 135 and it now 130 your fine

Edited by Bansh-eman
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hi all,

 

thanks for the responses. what do you think about the squish clearance. i think i am going to send them back to dave noss so i can get a tighter squish. i hear that .040 is the magic number. i don t want to run the motor cuz i can t return them to dave. i have a stroker / dune port, done by ct racing. i also hear that i am suppose to have about 155 psi to run pump gas. should i exchange the 21cc +2 domes for 22cc +2 domes? thanks

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i would try to get a tighter squish... this will bump your comp some too. you can run pump gas upto 155 psi. some guys will go farther then that but you have to pay more attention to the plugs and make sure your not detonating, at 155 i personaly run race gas or at least 50/50. its cheap insurance.

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