Question on 5hp Briggs 4 cycle Compression. Anyone know what it's supposed to be

[etbrown4]

This forum has the great and almighty chainsaw forum.

I thought that perhaps a few motormen might drop by here.....

I have a 40 year old 5hp horizontal shaft Briggs with what seems like low compression.

Curious if anyone knows what the hot or cold compression is supposed to be?

Many thanks for any help!

 

[Rivets]

I would normally like to see at least 90psi on the older engines. This will tell me if it is worth tearing into to get it running good. If it is below I do a wet test to see if it is just rings.

 

[etbrown4]

I would normally like to see at least 90psi on the older engines. This will tell me if it is worth tearing into to get it running good. If it is below I do a wet test to see if it is just rings.

Can you describe the steps in a wet test?

I've tried other air pressure leakdown tests before. Could see the pressure drop, but listening at the exhaust, intake, and the oil filler, I never knew reallly could tell which was leaking.

Tips appreciated.

 

[Rivets]

Wet test is done after you receive a low reading dry. To do a wet test squirt a small amount of motor oil into the cylinder and repeat the compression test. If the pressure increases, it is an indication the the rings are not sealing, as the oil helps seal between the rings and cylinder wall. If the pressure does not increase, that would indicate your leak is through the valves or head gasket.