I have a Honda mower with Engine GJAA-1345C43 MY2*. It had a stuck intake valve. Removed the valve and cleaned it up. Had it moving freely in the block. I put it together and adjusted the valves to spec's. Engine started on the first pull, ran great, mower about half the lawn when it started missing and popping. Removed the valve cover and readjusted the valves. Started first pull. Mowed about half the lawn today when it started bogging down and losing power. It will Idle but not rev up, it just bogs down. I think the valves are acting up again (haven't had time to check) Is this common for Honda's? Is there some trick to doing the valves so they stay set? I torqued the jam nut. The mower is only 3 years old. Any thought or suggestions will be greatly appreciated.

Check the rocker arm studs and make sure they are not backing out, If so remove them and add loc-tite.

Also check the rocker arms for wear in the bottom where the adjuster ball rides, They can wear thin and bend the center area of the rocker then eventually snap in half.

Good Luck