What is small engine repair?

Small engine repair refers to the maintenance, troubleshooting, and overhaul of small internal combustion engines typically found in lawn, garden, and other outdoor power equipment. Small engines power items like lawnmowers, generators, chainsaws, snowblowers, leaf blowers, pressure washers, and more. Keeping these machines tuned up and running properly requires specialized knowledge of small engine systems.

What types of engines are considered “small engines”?

Small engines generally refer to gasoline-powered engines that are lightweight and compact. This includes single-cylinder and twin-cylinder engines with displacements less than 30 cubic inches (500cc). Common small engine types include:

• 4-stroke engines – These have four cycles (intake, compression, power, exhaust). 4-stroke engines include gasoline engines found in lawn mowers, tillers, snow blowers, generators, and pressure washers.
• 2-stroke engines – Have two cycles (compression, power). These are lightweight engines typically used for chainsaws, line trimmers, leaf blowers, and some motorcycles.
• Single-cylinder engines – Contain one cylinder and piston. Many basic lawn mowers have single-cylinder engines.
• Twin-cylinder engines – Have two cylinders and pistons operating in tandem. Some motorcycles, generators, and snow blowers have twin-cylinder engines.

Maximum horsepower produced by small engines is around 25 hp or less. Displacements are typically less than 80 cubic inches (1.3 liters).

What are the major small engine components and systems?

Small engines contain a series of systems and components that work together to convert chemical energy from fuel into mechanical energy. The major systems and parts found in most small engines include:

• Fuel system – Transports and meters fuel to the engine. Includes the gas tank, fuel lines, fuel filter, carburetor and fuel pump.
• Ignition system – Provides timed electrical sparks to ignite the air-fuel mixture in the combustion chamber. Made up of spark plugs, magneto, ignition coil.
• Combustion chamber – The enclosed space where fuel is ignited and burned to move the piston. Contains the cylinder, piston rings, valves, cylinder head.
• Crankcase – Houses the crankshaft and lower end of the engine. Oil is stored here to lubricate moving parts.
• Crankshaft – Converts reciprocating motion of the pistons into rotational motion to power the machine.
• Valve train – Components that control intake and exhaust valve operation including valves, rocker arms, pushrods, springs, keepers.
• Cooling and exhaust system – Cools the engine and expels combustion gases. Includes muffler, exhaust pipe, cooling fins, flywheel.

Proper maintenance and repair procedures must be followed for each of these systems to keep small engines running efficiently.

Common small engine brands

There are several major manufacturers producing small engines for consumer outdoor power equipment:

• Briggs & Stratton – One of the world’s largest small engine producers. Makes engines for lawn mowers, generators, pressure washers, go karts.
• Honda – Renowned for high-quality, easy-starting small engines. Honda lawn mower engines are very popular.
• Kohler – Known for durable, high-performance small engines on lawn tractors, zero-turn mowers, generators.
• Kawasaki – Japanese company producing twin-cylinder engines found on riding mowers, ATVs, watercraft.
• Tecumseh – Produces L-head engines for snow blowers, tillers, chipper/shredders, commercial turf equipment.

These manufacturers produce both consumer-grade and commercial-grade small engines. Always check your equipment’s manual for the specific make and model number when servicing the engine.

Common small engine fuels

Most small engines are designed and tuned to run on a specific type of fuel:

• Gasoline – The most common small engine fuel. Gasoline (petrol) is a liquid hydrocarbon fuel that can be ignited in the engine to create energy.
• Diesel – Used in high-torque applications like cement mixers, airport ground support equipment, irrigation pumps. Diesel ignites via compression ignition.
• Propane – Used as an alternative fuel in certain small engines, especially generators. Propane offers a longer shelf life than gas but less power.
• Natural Gas – Used in small engine applications such as irrigation engines, generators, cement mixers. Requires a natural gas compressor and tank.

The proper fuel specified in the equipment’s operator’s manual must always be used. Never try to run a gasoline engine on diesel or vice versa due to the differences in how the fuels ignite.

Typical small engine repairs and maintenance

Small engines require periodic maintenance and will eventually need repairs. Here are some of the most common small engine repairs DIYers and technicians perform:

• Oil change – Drain and replace dirty oil to clear out contaminants and replenish lubrication. Should be done annually or every 50 hours of use.
• Spark plug replacement – Over time spark plugs become fouled or worn and require replacement. Replacing at the recommended interval improves starting.
• Air filter cleaning – A dirty air filter restricts airflow to the carburetor causing poor engine performance. Filters should be cleaned or replaced as specified.
• Fuel filter replacement – Clogged fuel filters block fuel flow causing issues with engine starting and power. Replacing annually prevents filter plugging.
• Carburetor adjustment – Carburetors regulate the engine’s air-fuel mixture. Adjustments help optimize performance and smooth running.
• Valve adjustments – Valves can become out of spec over time leading to compression issues. Adjusting the valve clearance offsets wear.
• Engine overhaul – Complete tear-down and rebuild of the engine. An overhaul is done when the engine has excessive wear or damage internally.

Following the manufacturer’s maintenance schedule, checking fluid levels, replacing filters, and using fresh fuel reduces the need for repairs. But engines will need periodic tuning and part replacement over time.

Diagnosing common small engine problems

Small engines exhibit common symptoms when something goes wrong. By recognizing the signs, you can begin diagnosing potential issues:

Engine won’t start

• Drained or old fuel – Empty fuel tank or stale gasoline.
• Faulty spark plug – Cracked insulator, fouled electrode, improper gap.
• Engine flooded – Choke left on causing excess fuel in cylinder.
• Dirty air filter – Reduced airflow chokes the engine.
• Broken recoil starter – Worn starter rope or spring.

Engine lacks power

• Partially blocked fuel filter or line – Obstructs fuel delivery to engine.
• Dirty air filter – Insufficient air intake limits engine power.
• Faulty carburetor – Incorrect adjustment or dirt in carb restricts fuel metering.
• Low compression – Worn piston rings or leaking valves reduces combustion efficiency.

Engine sputters or knocks

• Incorrect spark timing – Damaged flywheel magnets throw off ignition timing.
• Carbon buildup – Excess carbon deposits in combustion chamber cause pre-ignition.
• Low octane fuel – Engine “knocks” when burning fuel with too low of an octane rating.
• Overheating – Low oil level or dirty cooling fins causes engine to overheat.

Engine stops suddenly

• Out of fuel – Ran tank dry, causing engine to stall.
• Faulty kill switch – Switch is stuck in “off” position.
• Sheared flywheel key – Flywheel timing is thrown off causing shutdown.
• Spark plug failure – Intermittent spark stops combustion.

Diagnosing issues requires confirming the symptoms, systematically testing components, and process of elimination. Start with simple causes before testing more complex engine parts.

Safety tips for small engine repair

Working on small engines requires special safety precautions:

• Allow the engine to fully cool before servicing to prevent burns.
• Disconnect the spark plug before doing repairs to prevent accidental startup.
• Wear eye protection – debris can fly when engines are run or compressed air is used.
• Use jack stands when supporting equipment to prevent crushing injuries.
• Ensure adequate ventilation when running engines to avoid exhaust gas exposure.
• Avoid fuel spills and have an approved fire extinguisher on hand when handling gasoline.
• Use proper lifting techniques when removing heavy engine components like flywheels.

Following manufacturer’s instructions in the service manual is critical to avoid hazards. Allowing only qualified technicians to do extensive repairs reduces risks.

Small engine tools and equipment

Servicing small engines requires having an assortment of automotive tools plus specialty equipment designed for compact engines. Here are some of the must-have tools:

• Socket sets – For removing nuts, bolts, and screws on parts like blower housings, mufflers, and carburetors.
• Wrenches – Open-end, box-end, and adjustable wrenches to loosen fittings, lines, caps, drains.
• Screwdrivers – Standard and Phillips head screwdrivers for disassembling carburetors, ignition modules, and plastics.
• Pliers – Needle nose and slip joint pliers helpful for clutching rings, caps, springs.
• Spark plug wrenches – Required for removing/installing spark plugs in recessed wells.
• Compression tester – Screws into spark plug hole to measure combustion chamber sealed pressure.
• Multimeter – Tests ignition system components and electrical circuits for troubleshooting.
• Small engine stethoscope – Metal cone helps isolate internal engine noises during diagnosis.
• Telescoping magnet – Retrieves lost fasteners, parts from tight areas.

Having an organized toolbox with both standard and small engine-specific tools is key for DIY repairs. Quality tools allow you to properly disassemble engines and torque bolts during reassembly.

How to learn small engine repair

Here are some ways to gain the knowledge and skills for small engine maintenance and repair:

• Take a small engine repair course at a trade school. Hand-on training covers engine overhaul, troubleshooting.
• Apprentice at a shop to learn alongside experienced small engine technicians.
• Watch online training videos demonstrating repairs and diagnostics step-by-step.
• Purchase small engine repair books with diagrams and descriptions of procedures.
• Disassemble a damaged lawnmower engine to examine each component part.
• Join online forums and ask questions when you get stuck diagnosing issues.
• Get factory certified by a manufacturer – many offer certification programs.
• Start fixing your own equipment and build up hands-on experience.

Gaining familiarity with engine operation theory helps support the practical skills learned through disassembly and repairs. Both are needed to become proficient.

Small engine repair certification

Technicians can demonstrate their competency by earning industry-recognized certifications:

• Equipment & Engine Training Council (EETC) – Offers four levels of technician certification based on experience.
• Equipment & Engine Certification (EET) – Certifies diesel and gasoline engine mastery through hands-on testing.
• Briggs & Stratton Master Service Technician – Certifies expertise in servicing Briggs & Stratton engines.
• Kawasaki Engine Certification – Tests knowledge of Kawasaki engines used in turf equipment.
• Kohler Expert Level Technician – Certification program to service Kohler residential and commercial engines.

Many employers require certification for small engine technicians. Customers often look for certified shops when selecting repair services. Certifications demonstrate valuable expertise.

Career opportunities in small engine repair

Some occupation options related to small engine service include:

• Lawn equipment technician – Work for a power equipment dealer servicing residential mowers, trimmers, blowers.
• Rental shop mechanic – Maintain rental equipment like generators, concrete saws, aerial lifts.
• Marina mechanic – Service boat engines and integrated engine systems at a marina facility.
• Municipal mechanic – Maintain park equipment, generators, golf cart fleets for local governments.
• Chainsaw specialist – Focus on the unique repair demands of gas and electric chainsaws.
• Equipment restoration – Refurbish old engines and equipment back to original condition.
• Repair shop owner – Open your own small engine repair business.

There are opportunities to either specialize by machine type or work on a wide variety of equipment. Experience leads to senior technician and shop supervisor roles.

Benefits of learning small engine repair

Some advantages to learning DIY small engine service include:

• Saves money – Repair your own lawn mower and other outdoor power equipment at a fraction of the cost of taking it to the shop.
• Convenience – Service engines when it fits your schedule rather than waiting for an appointment at a repair facility.
• Customization – Ability to modify or enhance your engine performance for specialized applications.
• Self-reliance – Don’t have to depend on others when your equipment needs maintenance or repairs.
• Prevents damage – Well-maintained equipment lasts longer and avoids costly engine failures.
• Safety assurance – You control the quality and completeness of the repairs done.
• Universal skill – Small engine knowledge transfers across many types of residential and commercial equipment.

Learning proper small engine care lets owners get the most value from their equipment investments. Both DIYers and professional technicians benefit from these skills.

Conclusion

Small engine repair is the maintenance and overhaul of compact, single and twin-cylinder internal combustion engines. Mechanics service small engines in outdoor power equipment like lawn mowers, generators, snowblowers, pressure washers, and chainsaws. This requires specialized knowledge of small engine fuel, ignition, cooling, and exhaust systems. With proper tools and training, small engine repair skills allow both homeowners and professionals to service equipment efficiently. Gaining competency through hands-on practice and certification is key to becoming a qualified small engine technician. Overall, small engine repair is a valuable trade craft benefitting equipment owners, technicians, and repair shops.