Sudden loss of compression

Hi Mark,

Good idea to do another compression check before anything else. 

Yes will do. And I will check the rockers for free play.

Assuming the valve clearances are ok but compression is still low, do you see a risk of running the engine? I'm guessing carbon deposit could be hindering one of the valves  from fully closing but I don't want to risk burning the valve? Not sure how real that risk is? Perhaps running at idle until oil temp is 50C and then rechecking the compression could be a low risk attempt here?

Yeah, that's quite a few question marks but I'm not an expert so looking for some advice here.

Thanks!

Are you using 100LL or auto fuel? If the compression test is good and everything under the valve cover looks good then try a start, but do not let it sit and idle at low rpms.

Auto gas.

The compression for sure won't be good, that I can feel.

Mark...just forget about doing compression testing by cranking.  Do cylinder leak down.  You will hear bleed into the crankcase, with the oil tank cap off, that is normal.  If you are hearing leakage from the exhaust, bad valve seating.  if you hear leakage into the air intake, intake valve leakage.  The lifters are hydraulic and there is no valve lash to measure.  

Cheers