Iowa State University Extension and Outreach
Rapidly growing grass during the spring keeps lawn mowers busy. To ensure your mower is in good shape and limit downtime, it’s wise to review basic maintenance procedures.
It’s always best to start with a review of maintenance items for both engine and mower in the operator’s manual, hopefully with your mower but may also be available on-line. A general checklist follows, but individual mowers often have a peculiar location or two requiring lubrication or periodic inspection. Don’t forget to read through the safety section, often found near the front of the manual. It’s been six months since fall mowing and it’s a good idea to refresh memory on safety issues.
Adequate amounts of clean air, supplied to quality fuel, with a good spark for combustion are necessary for engine operation. Maintenance intervals for air filter and spark plug replacement should be specified in the operator’s manual. Replacement time is affected by hours of use and can vary from every two or three years for light use to multiple in-season replacement for large areas or commercial use. Homeowners with larger yards may replace filter and spark plug annually. Because lighter elements of gasoline volatilize through the off-season and viscous varnish can eventually be deposited in the fuel system it’s a good idea to empty the gas tank during the off-season and start out with fresh gas in the spring, or at least use a fuel stabilizer in the off-season to reduce varnish production.
Engine oil change is typically recommended on a more frequent basis than air filter and spark plug, perhaps several times during the season if significant hours are being put on the engine. Proper oil viscosity will be listed in the operator’s manual and the amount required for an oil change. Viscosity specifications are according to Society of Automotive Engineers (SAE) “weight” criteria. For example 5W30 is a multi-weight oil, acting as a heavier, more viscous 30 weight oil during warm summer afternoon temperatures and a lighter 5 weight oil at colder temperatures in early spring or late fall. Through the season, check engine oil level on the dipstick and add oil as necessary, but no further than the “full” line. Check inflated tire pressures periodically.
Many mowers transmit power to rotary blades and self-propelled drive wheels on the mower by rubber belts. Checking belts for signs of wear or cracks can avoid an unexpected broken belt midway through heavy mowing season in late spring. A sharp blade provides a clean cut to the top of grass and is more efficient for cutting. Operators should periodically inspect the quality of grass cut and blades for wear. Sticks, stones or striking other hard surfaces rapidly degrade blade sharpness. Rinsing the deck underside after use can avoid old grass buildup from hitting the mower blades or premature deck rust.
Lubricating grease or oil is often required at various locations on all but the simplest push mowers. A gear transmission associated with self-propelled drive wheels and steering spindles on rider mowers will likely have lubrication intervals specified. Belt idler pulleys should turn freely and may have a lubrication point. Larger, pull-behind rotary mowers using power from a power-take-off (PTO) shaft normally have a right-angle gear box requiring oil bath maintenance.
Remember safety issues. Take a couple of minutes to pre-scout the mowing area for obstacles such as sticks, stones, or debris that could become flying projectiles to bystanders or yourself. Wear closed-toed shoes (avoid sandals). Consider use of protective eyewear. Hearing protection is a good idea for louder engines, or longer exposure times. Leather gloves and protective eyewear are encouraged for maintenance and shop work. Safety interlock switches such as for operator presence and the transmission being in neutral at startup should be maintained.
Stability and rollover hazard is an issue on steeper slopes or when making a tight turn at too great a speed with rider mowers. Equipment often weighs more than the rider so crushing hazard is serious in addition to unprotected rotating blades. Slow down before making turns. On steeper areas consider replacing grass with ground cover that doesn’t require mowing.