Why Does My John Deere Riding Mower Smoke?

John Deere riding mower engines have much in common with the ones in push mowers, except they have more horsepower. For example, the D130 lawn tractor features a 22HP Briggs & Stratton engine, whereas many push mowers employ Briggs 5HP engines. When small engines smoke, the color of the smoke is an indication of the problem -- which can range from a dirty air filter to worn engine parts that need servicing.

The smoke coming from a small engine, such as the one in a John Deere riding mower, can be blue or white, which indicates that oil is burning inside the combustion chamber. Bluish smoke generally indicates a larger amount of oil combustion than white smoke. If the smoke coming from the engine is black, it's an indication of incomplete fuel combustion. The smoke is black because it's filled with carbon deposits leftover from the combustion process, and these are probably also collecting inside the engine, on the spark plug and air filter.

Unlike a two-cycle engine, which burns a mixture of oil and fuel and may generate a small amount of blue and/or white smoke all the time, a four-cycle engine, such as the one in a John Deere, has a separate compartment for the lubricating oil. Seals on all the moving parts confine the oil to the crankcase and keep it out of the combustion chamber. Consequently, blue/white smoke may mean that these seals have worn thin and need replacing. If that's the case, the mower engine also may have lost compression and may be performing poorly. The smoke can signify a temporary, minor problem -- you may be operating the mower on a hill, and some oil may have spilled into the combustion chamber.

Black smoke can be related to bad fuel, carburetor problems or a dirty air filter. The air filter is easy to check and clean or replace if it's dirty, but if the engine continues smoking, it may be because the tank is full of stale fuel. Old fuel tends to collect moisture, and that inhibits combustion. If you've changed the fuel and air filter and the engine still emits black smoke, the carburetor probably needs adjustment. It may have opened too wide -- which can happen after many service hours -- creating a fuel mixture that's too rich.

You should be concerned about blue or white smoke only when it occurs consistently for an extended period. If you see puffs of smoke, check the oil level -- you may have overfilled the crankcase, and you can stop the smoking by draining some of the oil. If the smoke is accompanied by poor engine performance -- especially loss of power -- you may have to have a service technician replace some engine seals. Although it's possible to adjust the carburetor yourself to stop the engine from emitting black smoke, it's probably more prudent to have this done by an authorized professional as well.