dsybert

I have a White GT1855 lawn tractor with a horizontal shaft twin cylinder 18hp briggs on it. The engine will start fine, idle fine, and run at full throttle fine. When you engage the deck, the rpms don't drop and everything is fine. When you try to cut grass or go up a hill, it loses power very quickly and will stall out if you let it get that far. When this happens, the governor is slammed wide open. No popping, or missing, just power loss.

I have checked the valve clearances, installed new head gaskets, checked the valve seats, replaced the fuel and air filters, checked the rubber diaphragm in the carb,, etc.

I'm not sure what to check next. The engine has alot of hours on it, but if it was so whipped that it couldn't even move on its own, wouldn't it smoke like a chimney? I cut grass with it once this year, and everything was fine. When I tried a second time, this power loss happened.

Any thoughts? thanks!