Have just done a compression test and piston 4 is at 50 Could there be any other causes than a knackered bottom end??

- worn valve seats

- sticking valves

- head gasket leak?

 

there may be other possibilities....

- worn valve seats

- sticking valves

- head gasket leak?

 

there may be other possibilities....

Worn Rings or cracked broken ring lands or burnt valve

Have just done a compression test and piston 4 is at 50 Could there be any other causes than a knackered bottom end??

Put a very small amount of engine oil in all the cylinders and test again to see if its rings. (wet test)

maybe your engine went on a bender like mine! this was the culprit for my low compression...