Advice on compression readings...

is it possible to inspect the sleeve without going to the base gasket ?

...measuring while the piston are at their deepest position ?

Anyway if it's not possible you can be sure i change the base gasket + hone + new rings. It's just because it will cost a little more

and well if go to this level i could get it bored and fit oversized rings.

laurent

TeK9iNe wrote:

Didn't you add oil and the compression came up?

That means it isnt the valves...

I typed a long explanation with examples demonstrating that your statement is incorrect, but then it hit me.

Is there anything at all that would change your mind?

A "Leak Down Test was mentioned, that is what you need to do if you want to know what is leaking. As far as rings, yes they will rotate, if you read about the machining process, the "Cross Hatch" pattern on the wall is part of what can cause this on a fresh bore/ hone job. That is why rings are staggered when installed to lessen the chance of alignment occurring later as it is "Seated". Pinning is common place in 2 cycle engines as well as for example Detroit diesels as these have exhaust ports instead of valves.

A "Leak Down Test was mentioned, that is what you need to do if you want to know what is leaking

Yes i know but Leak down test is the opposite of compression test. You induce pressure in the cylinders and you look for how much pressure you loose. But how it can tell you where it leaks? You will just know that you loose pressure (which i already know because of the low compression 121 psi).

I am right ?


thank you guys,


laurent

If its leaking you'll know it. You can hear it hiss. Or if its a head gasket ,take a spray bottle of soapy water and spray the area of the gasket any leaks will bubble.

If its leaking you'll know it. You can hear it hiss. Or if its a head gasket ,take a spray bottle of soapy water and spray the area of the gasket any leaks will bubble.

As a cheap version of a leak down tester i could use my compression tester adapter and inject 100 psi of compressed air into the cylinder and look for hiss and bubbles. Sure i wouldn't how much pressure I'm loosing but I've already know there's a problem with that cylinder.

EDIT: i think you can't know for the rings and side blown head gasket (not cylinder to cylinder)... like leaking internally where the cam chain is.

regards,
laurent

I finally found the who was the culprit for the low 121 psi on the #2 cylinder! The head gasket is blown...it's leaking pressure into the crankcase via the cam chain passage i can hear the hiss (valve cover removed) for pressure lost while rotating the crankshaft with a ratchet.

Thank you very much for everyone that participated in this thread ....

regards,
laurent