Honda GXV620 engine - uneven running
I have a 6 year old Hustler Fastrak mower with Honda GXV620 engine. Last season it was sometimes running unevenly and lacking power - unsteady noise from the engine - and would slow and almost stop with the blades turning on an incline. I changed the air filter and foam filter and that seemed to fix the issue. It then started again right at the end of the season. I could simply remove and replace the same filter and the next time it would be OK.
Over the winter, I replaced the air filter, fuel filter, spark plugs, but when I had completed all that, the first time I started it, it still stuttered, but I put new gasoline in, and the next start was fine. I did a bit of mowing and put it away. This morning - same thing - uneven, lacking power.
I hadn't checked the spark plug gaps, and so I took one out, checked it (OK) and put it back in. Next start - it was fine and I mowed for an hour.
I'm not confident that I have actually found the issue though - it almost seems to be that doing something around the engine fixes it, but after a rest, it is back to low power again!