It's not super complicated. The X and O chart saves a minute or three over setting each cylinder to TDC compression and adjusting both valves.
That's what I recommend for inexperienced owners.
Take all the plugs out, they make it tricky to set at TDC because of the compression.
Take all the tappet caps off.
Remove the round alternator cover. Use the flywheel (rotor) bolt head to turn the engine over - turn forward (CCW on the alternator) as turning reverse makes these instructions useless plus you will be also turning the starter motor - making rotation quite difficult.
Don't use the points cam nut unless you're very familiar with how much torque it will take before it breaks (not much). If you break it there will be much unfun. The rotor bolt should be tight enough to turn the engine over without coming loose but don't really reef on 'er.
Turn the engine while watching the rockers on #1, when the intake rocker moves up (valve closing) keep turning (~1/2 turn) but look in the advancer and watch for the 1-4 mark lined up with the pointer. It will be #1 TDC on compression stroke: both valves fully closed so their tappet clearances can be adjusted. (#2 & #3 will be at BDC on intake or power stroke... one each of their tappets can be adjusted - that's the X and O business - I think this TDC compression stroke only adjusting method is simpler to remember and only takes a bit longer)
Adjust #1 tappets, intake and exhaust.
Turn the engine one full crank rotation back to 1-4. This has #4 at TDC compression (it was at TDC exhaust before, with the exhaust valve just closing and the intake valve just opening... neither adjustable)
Adjust #4 tappets, intake and exhaust.
Rotate crank and watch the #2 intake tappet, again when it moves up rotate to the 2-3 mark. Adjust #2 tappets. One more turn back to 2-3, adjust #3 tappets.
Replace covers. Ride on.
Make sure the tappet lock nuts are TIGHT. These are hardened nuts on hardened tappets through hardened rockers, they will take a lot of torque and still be smiling. It's bad if they vibrate loose, and the rockers really shake. Take my word that you don't want to be looking for a nut and maybe tappet that dropped down into the main case.
Your feeler should be dragging - not free and not stuck tight - with the nut tight. This is a learned skill, leaving the "screw" just a bit too tight and then pulling it back to where the feeler is snug by tightening the lock nut.
Don't overtighten the tappet covers. The sealing is by the O-ring, just tighten enough that the caps won't rattle loose. These are a bugger to get off if overtight, and the 17mm head section will crack right out of the dome if overtorqued either direction.
