I am having a problem with my engine surging when under heavy load. It runs fine until I get to thick high grass and then it will start to surge. When I get out of the tall grass it returns to normal. Any help would be greatly appreciate.
Valve adjustment
dirty air filter
fouled plugs
dirty engine block and cooling fins
dirty fuel tank
deteriorating fuel lines
plugged fuel filter if installed
dirty carb most likely as Scrub said.
When it starts to surge pull the choke out gradually and see if it quits surging. If it does you have a fuel delivery problem. Make sure you are get ample fuel to the carb,pull and clean the carb. Fuel filter could cause this if it just starting to stop up,
