Lawn-Boy has significantly re-engineered its two-cycle lawn mower engine to exceed EPA emissions requirements. In addition, the new DuraForce engine is more powerful, easier to start, and easier to service and maintain than the engine currently found on Lawn-Boy's Silver Series mowers. Lawn-Boy is the only remaining domestic manufacturer of two-cycle engines specifically designed for lawnmowers.
The new engine achieves a 50% reduction in emissions compared to its predecessor due to a number of improvements. These include a leaner, 50:1 fuel/oil ratio; boosted port scavenging (a third intake or "boost" port improves combustion); a projected-nose spark plug; and a two-circuit, fixed-jet carburetor. The resulting engine produces dramatically less visible smoke and consumes about the same amount of oil as a typical walk-power mower with a four-cycle side-valve engine.
Lawn-Boy engineers took special care in designing the engine for long life. The air cleaner is 48% larger and uses a precleaner system that takes advantage of air intake inertia to maximize airflow and to prolong the life of the air cleaner (and, therefore, the engine it protects). The main filter element is reusable. More cooling fins are added to the cylinder wall, and a polymer-bodied carburetor is used to prevent corrosion. Other life-prolonging features include a cast iron cylinder liner, an oversized crankshaft that rotates on twin ball bearings, a beefed-up connecting rod, and improved bearing lubrication.
Thanks to a larger 141-cm3 displacement and the boost ports, the engine produces 4.8 kW(6.4 hp), compared to the current V-engine's 3.5 kW(4.7 hp). More power and a flat torque curve mean that more efficient cutting and mulching are possible in tough conditions.
