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I have a 1600 kent engine and completely rebuilt the motor about 2000miles ago (new rings, bearings, laped valves, engine hone etc.)Today, I did a compression test and noticed that cylinder 1 and 2 are alright - 145psi - whereas cylinder 3 and 4 are at 115psi.

I read somewhere that 145 is low for a kent engine but I don't know if that's true or not.

Any reasons what it might be? Could a head gasket cause this? (there is a little oil seeping from the head gasket but no water in the oil at all). I hope it's not the rings not seating properly. Is there a way to fully determine this? I had an issue the other day where it wouldn't start, and then to it not idling properly - it would just die. Now I got it running as it should now but the low compression still bothers me.

I'm just looking for any advice.

Thanks,
Daniel

Put some oil (3-4 squirts from an oil can)through the spark plug holes into the low cylinders
If the compression comes up it's probably rings, if it doesn't change then leaky valve or head gasket.

Check valve clearances..if no clearance then maybe valve not seating.

Dave.

Dave C wrote:Put some oil (3-4 squirts from an oil can)through the spark plug holes into the low cylinders
If the compression comes up it's probably rings, if it doesn't change then leaky valve or head gasket.

Check valve clearances..if no clearance then maybe valve not seating.

Dave.

That's the way to check. Realistically, the actual figure is less important the lowest figure being within 90% of the highest, which isn't the case here. A compression test should be carried out with the engine hot and the throttle fully open.