Valve seals shouldnt see any pressure because the valves are closed and should hold way more compression than that engine can build. Valve seals are on the stem above the seats.
The auto decompression actually works on engine rpm. So how it works is the mechanism spins and catches on the plunger that the spring keeps tension on. Holding on a tab on one of the rocker arms and pushing a valve slightly open. Once the engine warms up the rpm raises and the oil pressure build and it causes the outer part to slide down off the plunger and lets the valves function like normal from then on.
Dang! What do they run on ebay up there?
https://www.ebay.com/itm/Four-4-Kenda-Executioner-ATV-Tires-Set-2-Front-26x10-12-2-Rear-26x10-12-K538/141722865639?hash=item20ff574fe7:g:sO0AAOSwQYZWymQF