i want to find out if my piston rings are knackered by using the compression tester how will i no .because i also heard from a mate the compression tester tells u if ur valve stem seals are worn.what do i look for.

 

Look for the reading on the gague.

If its low then the head has to come off so it matters not really, as it will be a rebuild time.

 

The compresssion test does not test the stem seals, it can indicate if the valves are not sealing well in the head valve seats. The stem seals are for oil control. If you have a low comp reading squirt some oil down the plug hole and repeat test if the reading improves it indicates ring / bore wear which as previously stated means rebuild time.