ive never seen any videos on it..but who knows. Pretty easy to do...just like any engine. on cold engine check the rocker arm of valve that isnt compressed. the preferred top dead center ON COMPRESSION STROKE method. generac manuals specify clearances and rocker arm torques.
IF YOU CANT tell the compression stroke from the exhaust stroke, you can use the "one up and one down method.". Ive tried both, and they both give good results. If one valve is down (open) then the other valve for that cylinder will be on the base of the cam and closed. This closed valve can then be adjusted. The process repeated for the remaining valve on that cylinder.
the hard part always seems to be needing to redo it 4-5 times as the gap usually closes after jamb nut it tightened. takes some practice. always follow torque specs as there aluminum heads and can strip.
over the years ive had to repair some units where the owners have twisted the new spark plugs in so tight, they strip the block. these too have a torque rating..and so too for the 4 bolts that hold the valve cover in-place. hand tighten only. the valve cover gaskets are reusable if care is used during removal of cover.
i can't recall at the moment what the rating is, as there on a cheat sheet in my repair tool kit on my service truck.
Mechanics "feel"...... sometimes not easy to capture precisely in words, let alone to execute consistently. Thanks again for the excellent description above.
In my teens, after realizing that I tended to over-tighten things, I bought a Craftsman 1/2" drive click-torque wrench for automotive work. Even with my tiny income at the time, it paid for itself quickly.
A lot of years later, one of my best purchases was a good-quality (Precision Instruments IIRC) 3/8" split-beam click-torque wrench, covering up to something like 500"/lb. When I looked around, there was a lot of junk 3/8 Tq wrenches on the market. Next target acquisition is a good 1/4" click-torque wrench, likely split-beam.
For an amateur wrench (me), I have a reasonable feel for mid and higher torque automotive fasteners. For lower torque stuff, it is deceptively easy to seriously over-torque small fasteners - at least for me, on things I don't do often, and working late, tired, distracted............ It's way cheaper and faster for me (completing a job successfully) to have good quality torque wrenches handy.
Rgds, D.