Lawnboy Supreme with D engine surges

[bwright1818]

It runs smooth when not moving or cutting anything. However, if it bogs even a little on heavier grass, it starts to surge and won't come out of it until I just stop and let it sit there. I cleaned the carb, even tried another clean carb. It has good fuel flow from the tank and the vent in the cap is clear. I even tried mowing with the cap a little loose. This is a two stroke, D engine with a metal body, Walbro carb, which has a true choke. No primer. These carbs have a screen in the nipple of the carb, which I removed and put in a new, Briggs type, inline filter. I put a new lower crank seal in. Still surges. It acts a lot like a Duraforce surge, but it has a different cab than that. I have been a hobbyist Lawnboy geek and a marine mechanic professionally, for over 50 years and this one has me stumped!

 

[Fishnuts2]

Have you tried turning the "altitude adjusting screw" if it has one on the Left side of the carb?

 

[Tiger Small Engine]

It runs smooth when not moving or cutting anything. However, if it bogs even a little on heavier grass, it starts to surge and won't come out of it until I just stop and let it sit there. I cleaned the carb, even tried another clean carb. It has good fuel flow from the tank and the vent in the cap is clear. I even tried mowing with the cap a little loose. This is a two stroke, D engine with a metal body, Walbro carb, which has a true choke. No primer. These carbs have a screen in the nipple of the carb, which I removed and put in a new, Briggs type, inline filter. I put a new lower crank seal in. Still surges. It acts a lot like a Duraforce surge, but it has a different cab than that. I have been a hobbyist Lawnboy geek and a marine mechanic professionally, for over 50 years and this one has me stumped!

Enlarge the pilot jet as a last resort if no air leaks, etc.