Well if it's the valve, it should be underneath the valve cover...?
Not trying to get smart with you, but I just had a similar issue with a brand new Kohler 15hp, and the valve cover is a bit interesting to locate if for no other reason than I haven't a clue (thou it's in your face), but once that came off it was about the same principle as a car.
Being that a blower has that vertical turbofan, I would assume it uses a horizontal shaft engine, the spark plug being on top would confirm this, the piston thus moves straight up and down if the blower is sitting flat (as it normally sits) on the ground... Thus, the valve cover should be located near the spark plug, top of the engine, you'll have to remove that big orange cover first, take it from there. Oh yeah, forgot to mention, the stupid rope coil start assembly, too (holds part of the cover), 3 bolts.
Take your time, and be prepared to run off to a parts store to get some liquid gasket, I had to reseal mine with some heat-resistant pcv junk, but you won't know that until you're into it, either way it's not that bad, maybe 4-8 bolts or nuts, then pry it off carefully... In my case, one of the nuts that holds the rocker arm had come off...
I put mine back together but it takes 24 hours for the junk to cure, so I'm not starting it till tomorrow, hopefully it will hold up.
It just gets to that point you got nothing to lose, if you can't find anything out of place then put it back together or keep digging.
