Hi
You can sometimes get away with it from what a few guys have told me over the years but have seen a few go wrong too. Brian will say never do it.

I just bought a super major that was supposed to need a head gasket. It was running on 3 cylinders

. on removal of the rocker cover it was found to have a bent push rod on one cylinder and a broken one on the next

. on removal of the head it was found that one piston had 4 slots gouged out of the piston crown where it had been spraying hi pressure fuel and not burning it.
They had run it so long I need to change the piston/ and push rods/ I'am also hoping that the crank is not damaged when I get the oil pan off
Long story short the guy that had this one needed a kick in the privates and NO I WOULD NOT USE THE DECOMPRESSOR

After finding this I 'am thinking i would lock the levers permanently or cut the end off on any I sell for acreage guys to use so they cant mess the motor up
I hope that answers your Question and ill post pictures of my wreck when I get chance
Regards Robert
A Fordson is for life not just for Christmas !.