Under certain conditions, grass clippings can clump up during mowing and sometimes clog the discharge system of the mower. If this symptom occurs, there are several factors that may be contributing to this problem:
Clean underneath mower deck if dirty or caked with grass
If the underside of the mower deck is dirty with old grass or other debris, there may be insufficient air flow to properly discharge or mulch clippings.
Run engine at full throttle
Running the engine at full throttle not only provides the air-flow needed to cool the engine, but also ensures adequate air-flow is delivered underneath the mower deck to properly discharge or mulch clippings.
When possible, mow when the grass is dry
After heavy rains or in damp conditions, grass can contain a significant amount of moisture even if it appears dry. Wet grass can result in poor cutting and clumping of clippings. For best results, ensure the grass is dry prior to mowing.
Avoid cutting grass that has grown too tall
Attempting to cut grass which has grown too tall can result in more clippings than the mower can properly discharge. The maximum height to effectively cut is 4 ½ inches. Set height adjusters so only the top third of the grass is cut. If grass is longer than 4 ½ inches, to wmowings will be necessary.
Cut grass while walking at a medium pace
Attempting to mow grass while moving too quickly may result in overloading the capacity of the mower to discharge of mulch clippings properly. Make sure to mow at a even, medium pace while keeping the engine running at full throttle for best results.
Keep cutting blades sharp and balanced
Mower blades should be periodically sharpened and balanced for optimum cutting and air-flow production. If you notice that the ends of your grass turn brown following a cutting, it may be time to sharpen (two times a year or after every 25 hours of use) or replace your blade if damaged (or every two years).
Make certain the mulch plate is installed in the mower's deck if mulching clippings
If the mulch plate is not installed in the mower deck, air-flow will be disrupted and the grass clippings will not mulch properly.