Had one that had a miss just like you described.After adjusting them twice,It was still missing,So I'm standing there scratching my head and decide to do the redneck thing,I started er up and pushed and wiggled the valves with my fingers,I think it was on number 5 the miss went away when I was applying pressure.Turnes out the valveguide was bad on the one cylinder.An easy fix and the motor was as good as new!!Tom
