Low compression issue

joem4790

New Member
I've got a 79 CB750 that's mostly stock except for GSXR carbs, 4 into 1 header, and cbr600 coils. I started having issues with no fire on cylinder 4 after a few rides. The bike ran great for a while but the misfire issue slowly got worse. Spark is good, I'm getting fuel but compression on cylinder 4 is low compared to the others and below spec. I just checked my valve clearances and the attached picture is what I got. All but cylinder 3 are way too tight.

What would cause me to have low compression on only number 4 if the other valves are also out of spec? Shouldn't I show low compression on the others as well? My first thought was rings but now I'm not sure.
 

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