Small Engine Repair Manual 5.5 HP - 20 HP 4-Stroke Engines

• Briggs and Stratton L-head and OHV Vanguard
• Tecumseh/Craftsman L-head and OHV
• Kohler K-series, Magnum and Command
• Honda OHV single-cylinder and V-Twin
• Robin/Wisconsin Robin L-head and OHV

MUFFLER REMOVAL AND INSTALLATION Note: Some mufflers screw into the engine, while others are attached with bolts. If the muffler is in good condition, it can be cleaned by tapping it with a soft-face hammer and dumping out the carbon that's dislodged. SCREW-IN MUFFLERS

1. To remove a screw-in type, first apply penetrating oil to the threads and let it sit for several minutes. You may have to tip the equipment to do this.
2. Try to remove the muffler with a pipe wrench by turning it counterclockwise (see illustration 2.2). Some mufflers have a lock ring that must be loosened with a punch and hammer before turning the pipe. Others have a built-in hex to accept an open-end wrench (usually there's not enough room to use a pipe wrench with this type).
3. If it breaks off, try to remove the part left in the engine (if there's enough left to grasp with the wrench). If it won't come out, use a large screw extractor or cold chisel to remove it. The muffler material is fairly soft, so don't damage the threads in the engine.
4. Screw in the new muffler, but don't overtighten it. If a lock ring is used, tighten it with a hammer and punch. Note: In order to prevent problems removing the muffler in the future, apply a thin coat of anti-seize compound to the threads of the exhaust pipe where it enters the engine.

Before proceeding, be sure the fuel tank is filled with fresh, clean gasoline, the fuel shut-off valve is open (if equipped) and fuel flows freely through the fuel line. Check/ adjust the mixture adjusting screw (if equipped) to make sure it's open and make sure the choke closes completely (see illustration 3.7). If the engine won't start, remove and check the spark plug. If it's wet or fouled, it may be due to:

a) Stuck chock b) Overly-rich fuel mixture c) Water in fuel d) Inlet needle valve stuck open (not all carburetors) e) Clogged muffler f) Plugged crankcase breather g) Too much oil in crankcase h) Worn piston rings

If the spark plug is dry, check for:

a) Leaking carburetor mounting gaskets b) Gummy or dirty carburetor internal parts c) Inlet needle valve stuck shut (not all carburetors) d) Damaged or deteriorated rubber diaphragms in carburetor (not all carburetors) e) Plugged fuel line or filter (not all engines) f) Failed fuel pump (not all engines)