Donki

[Donki]

Is 145 psi to low compression on all cylinders 

[datzenmike]

Higher is always better but as long as they are all close to the same say within, 10% of each other the engine will run smoothly. Say you got 135, 140, 145 and 150 compression readings. Take the highest as 100% thus 135 X 100/150=  90% which is within 10%..... close enough to pass. High compression numbers indicates the engine will efficiently capture more of the expanding gas energy.

 

Burning oil doesn't always mean the compression is bad and a lower compression cylinder does not automatically mean it will burn oil. Even engines with good compression can 'burn oil'. Worn valve guides or valve seals can eat huge amounts of oil.

 

Compression testing should be on a fully warmed up engine. Some pull the coil wire off and open the carburetor fully and take all the plugs out. The engine will turn faster but the readings are not what the engine runs under when running. I just do each cylinder in order, plugs in and carburetor closed. I'm looking for similar readings not anything absolute.

 

Write down the readings then pour a couple of teaspoon fulls of engine oil in the hot cylinder. If the compression is low from worn rings the oil will temporarily seal them and the reading will go up significantly. If no/little change, the loss is likely the valves are worn/broken/burnt and not sealing. Two adjacent low readings could be the head gasket between them is blown.