My HRX2174HYA with 215 hrs starts good and runs great, but the sparkplug tip is black. Not wet or caked-on carbon, but also not gray or tan.
I recently adjusted the valves and the exhaust was quite loose (.35mm), the intake was slightly loose (.18mm), I have not run it since then to see if this makes a difference.
I am at 540' elevation and the air filter is clean, oil is not overfilled. My grass is thick and tough, so it works pretty hard when I mow.
Could I change to a #65 main jet to fine tune the mixture or would that risk a meltdown? I think is has a #68 now.
