Yamaha F150 low compresion

Yamaha Mike

Recruit
Joined
Apr 17, 2021
Messages
2
Hello,
I was changing the spark plugs on my 2004 Yamaha F150 and thought it would be a good time to do a compression check. A few years ago it was 185 on all cylinders, today it was different. Today, cylinders 1,2 and 4 were 180-185, but cylinder 3 was 140. Not good, I went ahead and did a leak down test and cylinders 1,2 and 4 were 10-15%, but cylinder 3 was 50%. I could hear the air escaping from the left side of the engine. I pulled the thermostat and popit valve out of the cover and could feel the air coming out of the there. Engine had been running normal. What are your thoughts? Head gasket going bad?
 
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