I have an old John Deere 111, circa 1980, that seems to lose power when the blades are under an insignificant load. I'm not cutting very tall or abnormally heavy grass -- just your run of the mill yard here. The blades have been sharpened on a bench grinder and tested for balance. I've test the deck pulleys and they swing freely. Oil changed, cleaned the carb, and replaced the fuel filter.
When I engage the blades and without lowering the deck, they run at full power -- though it does leave an uneven, choppy cut on the grass. Now, when I lower the blades less than an inch, I can sense the blades not rotating at full power. The quality of the cut looks about like that of a mower being overloaded and choked out, but the engine runs fine the entire time. The quality improves when I reduce the speed to a snails crawl (2 of 5), but it is by no means perfect.
Does anyone have some advice on to why my mower is cutting poorly and also losing power when I lower the deck? I know this is a smaller JD, but this is ridiculous. Thanks for your help.