shaggyzr2
Active member
Hi, just picked up a 2000 SRX 700, the guy says the engine was rebuilt about 1500 miles ago, about how much compression should it have? I did a compression test on it yesterday, came up with just a hair under 120 psi on all three cylinders, I'm thinking that's a little low for a somewhat fresh engine, but it could be my guage, every engine I've tested seems to be lower than it should be. I've heard that many different compression testers will have different readings.
Good compression. Mine reads 110 - 115 - 115. Runs fine.
shaggyzr2
Active member
Is there a right way and a wrong way to do a compression test?
Yes. Get a good, calibrated compression tester. Take all spark plugs out. Hold throttle wide open and pull until the gauge doesn't go any higher. Usually about 5 good, brisk pulls should do it. Important things is that all cylinders are within 5% of each other. I have seen motors run with 80 psi. You're good to go.
shaggyzr2
Active member
Ok, I didn't have the throttle open when I did the test, and my guage is a cheaper one. Thanks
trailanimal
New member
you want to hold the throttle wide open when you are pulling over the engine try pulling the same speed for each cylinder and same number of pulls 3 or4 pulls for each.
Devilin AblueDress!
New member
Some guys say to take the belt off for less drag. Aftermarket gasket sets come with a thicker base gasket. Basically raises heads which lowers compression. All being similar is what your shootin for.
snomofo
VIP Lifetime Member
shaggyzr2 said:
Pull the plugs and belt if you prefer and ignition off. I usually only tug once or twice to max out the gauge (about 4-6 revolutions or pressure increases on the gauge per tug).
Cold engine values will be lower due to cold oil making it harder to pull but if all are within 5% you're usually in good shape if you're within a debateable 4K-6K+ rering schedule.
I've not seen substantial differences between throttle open or closed.