compression (in psi): #1 166, #2 149, #3 168, #4 164. #2 cylinder spark plug threads were previously damaged. I (somehow) rethreaded them (ie I don't remember how). I hear a hiss when I check compression, but can't tighten the compression gauge any tighter. I ran a tap through, and that got stuck halfway in. The threads appear clean and I wiped them with cleaner anyway. There's no oil in my coolant, no coolant in my oil. No smoke. What's with cylinder #2? Oh, the spark plug was white in color for #2, bronze in color for #3, and normal for #1 and #4