For the Polaris snowmobiles I picked up this spring, I checked them after doing top end checks/gasket replacements. I know, should have done the compression checks first. All four cylinders read 100. I took both plugs out of each motor, then with the compression tester pulled the cord 5 or 6 times. Is there a more accurate reading possible, like if I start the motor with the non-test plug still in place to allow it to run, albeit half-powered?
I've read they should be at or above 120, but is it really that serious to let them run at that compression a few more years? The rings, piston tops and walls, and the cylinder walls all looked fine - on the '93 Deluxe with 7,700 miles. Can't say the same for my '90 Indy as the head unit wouldn't budge. The guy's son said he put over 100 miles on it the weekend I picked it up after his trip. The piston tops looked fine, and so did the exhausts.
As I plan to keep these plenty more years, I'll budget next year for the .010 boring, new pistons with pins/rings, and gasket kits.
100 compression with new gaskets only - how long still okay