The Stovebolt Site Forums The Shop Area Engine Shop What do you think of my plugs?

If the mix was to lean wouldn't the base ring also be 'clean'? Seeing that all 6 plugs show some carbon on the base ring tells me that the mix is *maybe* at the upper end of of proper range.

The heat zone on the center electrode also looks to hot (not mixture wise, but heat zone wise).

Maybe go down in heat range on the plugs?

Does the motor ping under load?

The original AC-44-5 plugs were mid heat range... like a 4 or 5 on a scale of 1-10.

The rj18yc6 seems to be a hotter plug rated 6-7 on the 1-10 scale. Maybe try rj12's or rj14s and see what looks (and runs) better.