Riding mowers are effort and time savers, a particular plus on hot days. Kohler engines power numerous manufacturers of riding mowers and have established themselves as reputable little engines for mowers that have to cope with dust, sand, sea air and an occasional downpour, in addition to warm summer air. Whenever your mower flames and then dies, the cause may be ecological, fuel-related or the result of a technological problem.
Extremes in temperature during hot summers, fog and soggy weather can all provide clues to a mower’s failure. Hot weather can contribute to vapor lock stalls, particularly with an improperly vented gas tank cap. Moisture at a fuel supply, in the gas tank or can, can stop an engine.
Always follow your mower’s operator manual recommendations for fuel and filters — and stick to the prescribed maintenance program for replacement. After inactivity, the gasoline on your mower’s tank starts to break down and lose volatility. Drain the tank, protecting any sediment, and refill with new fuel so the motor “catches” easily when it flames. Inappropriate fuels, such as diesel which won’t burn properly or gasoline with over 10 percent ethanol that can damage engine parts due to high heat, can also cause failure to get started. A fuel line obstruction, clogged fuel filter or adhered fuel valve shutoff may cause irregular or insufficient fuel supply to maintain combustion. Even though the motor may fire as the result of the spark in the solenoid, not enough fuel feeds during the carburetor to maintain continued combustion. A flooded engine, because of an open choke, can result in an engine to fire and then die — the smell of gasoline provides a cue to flooding.
When the solenoid has supplied the spark to fire the starter, then the carburetor, spark plug and pistons carry over. Although little engines are simple, they rely on every component running at a perfect rhythm. In addition to fuel obstructions, a spark plug having an improper gap or one that is loose won’t maintain combustion. A broken flywheel key — the component that creates the charge for your spark plug — from impact or wear, can’t support combustion. A bent shaft or unbalanced knife throws off the balance on the crankshaft, eventually retarding piston and cycle timing, leading to misses and stalls rather than starts.
If you attempt to start your mower without putting the gear lever in neutral or depressing the brake pedal, the starter may burst, but your motor will choke. The exact same holds for transferring the seat off, which opens the “kill” switch, an essential safety feature in all mowers. Many causes of the engine that flames but refuses to start are easy to tackle, but you can be fatal: failure to maintain lubricating oil in the appropriate level in the crankcase and its pistons. The motor may run until the oil level becomes too low to maintain the piston lubricated. Following a run of rough starts, the motor will fire but freeze rather than start, signaling seized pistons.