1.9l audi SD motor

[DVR68U]

hey guys i have a SD motor in a mk1 and i did a compression check and found i have 150,150,150,125.
what do you guys reckon it is , valve or rings ?
its been run on a basic carby conversion that a pre owner has put on and ran like balls. maybe it leaned out and burnt a valve.
cheers brenton

[Golf Loon]

Put a capfull of engine oil into the cylinder and test again. If it improves, its rings

[twin eng, twin turbs]

Even just looking at your spark plugs if a valve is burnt out it will be noticably different and your engine will run ruff as guts! 25psi less is not the best but it is not to bad it is probably just rings on the way out. If you put that cap of oil in and the rings are fine the compression pressure will go up but if you find the compression pressure stays the same its because the oil has run down past the rings into the crankcase and they are in need of replacement..

[DVR68U]

hey just wanted to up date , i did another compression check and after runing the motor some more it came up to 175psi once warm the same as the others. could have been a sticky valve or some grit in the way. seems to have done the 8v 9 lives trick and fixed itself lol
cheers brenton

[Jmac]

Some upper cylinder lubricant in order here i think maybe got some carbon stuck in there. Subaru foam upper cylinder lubricant is the bollocks for that
Cheers
Jmac

[DVR68U]

ill keep that in mind if i get the problem again. cheers brenton