Compression Test Results - Recommendations?

[vesnyder]

Having issues with one particular cylinder and did a compression test:
#1 - 90 psi
#2 - 120
#3 - 120
#4 - 125

The cylinder I was having issues with is the 90 psi cylinder - was not firing? Replaced the plug and it seems to run fine? Everything I've read states that they should be close - I assume closer than this? I need to recheck the valves, but what do you recommend?

[Dave at Pelican Parts]

Re-check the valves, re-test all four holes. Maybe try them all cold. If they are still fairly uneven, try a leak-down test. Or at least see if you can set the low cylinder to TDC and jam an air fitting into the spark plug hole (rubber tip of course!). Then listen for where the air comes out; exhaust pipe or intake snorkel or oil filler...

--DD

[John Rogers]

If you had a cylinder that was not firing then any oil on the rings will get washed off from unburned gas and they will not seal as well. If it were mine, I'd drive it a bit, easily making sure the cylinder is firing okay all the time and then retest after a few days to see if the compression came up. I think it will although maybe not quite as high as it should due to the accelerated wear.