Did a compression check on the motor in my Advantage and its running around 125 - 135. The motor is supposed to be 9-1. I would like to start the Rogers project that I bought on E-bay last year and decided to do a compression check on it. The first cylinder I check was 190 , the rest were 180+ except for one at 150 .Am I correct in taking the 135 dividing it by 9 =15 lbs, then taking 180 divided by 15 = 12 to 1 comp. ratio, or is there some kind of sliding scale?