did this last year and had a valve job done, shop said its the valves, so new valves and seats, still hard to start but ran good for 200 mi. and it sat for a week and no compression again, could it be valve guides, was hard to start hot let it sit 10-15 min. and it would start and run good, set at TDC, took out plug, put tissue paper over muffler out let, air box intake and crank case breather, blow compressed in plug hole, paper over air box moved a little, paper over muffler outlet flapped like crazy, gave it 100 psi and air box stopped, muffler went crazy. valves holding open, also if u tow start it starts right up,

 

Firstly, when you did the leak down test, are you sure you were on TDC on the compression stroke? Then check the valve clearances. The new seats may not have been properly hammered home and, if they sunk a bit with use, the clearance will have gone.

 

valves checked before test and still were set correct, TDC for sure, also turned crank 360 4 times to make sure and lined up tdc mark on crank every test, stuck long screw driver in plug hole to find tdc, watched valves open and close and made sure they were loose when testin,

 

Hmm value seats new? what type head is this? Need to measure guides to see if clearance is correct also is values dirty with ols fuel residue on stem.Was ols values bent or just worn out?

 

new valves and seat put by motor shop, only 200 mi. on and was in 2 days, going to pull head off and send back to shop (different shop) to if they say

its needs valves and sets like the other shop said the last time.
u know most shop are like cops, they only need a few seconds to figure whats best and easiest for them.