Lucas B&S engine searching

[sawguy21]

With those compression readings I am surprised it cranks over, either the valve lash is too much or the ACR on the cam has failed.

[Don P]

Ah thanks for that. Valve lash is adjusted to spec intake and exhaust (.005 IIRC) 1/4" past TDC which is their spec location. I did notice and wonder about the "bump" in the rocker motion on the 120 psi side when rolling it over by hand. I guess that would be the automatic compression release... or the remains of it. I'm guessing if it were operating correctly, at starter speed I shouldn't have been getting much of a reading so something is up. Need to pull the other valve cover and see if that motion is there on the other side. You got me googling, this seems to be a weak link in their valve train. I'll see if I can get a magnet into the sump and look for parts. No cranking power issues though, it seems to spin up fine.
I did see racing cams for it while googling  :D

From B&S

The compression release system lifts either the exhaust or the intake valve slightly off its seat during the compression event (this is why the piston is positioned past top dead center to about 1/4" down from the top of the cylinder when adjusting valve clearances). This releases pressure and reduces the force required to pull the starter rope or load on the starter motor. A compression release is used on most Briggs & Stratton engines and does not affect engine performance above engine starting rpm.