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Home / Small Engines / Kohler Engines / Kohler CH12.5S

Kohler CH12.5S Troubleshooting

Engine Model: Kohler Command CH12.5S

Engine Type: 4-cycle 1-cylinder air-cooled gasoline engine

Total Displacement: 24.3 cu.in (398 cc)

Rated Engine Power: 12.5 Hp (9.4 kW) at 3600 rpm

Carburetor Type: Adjustable or fixed main jet

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Engine won't start or hard to start

Fuel tank is empty - Add fuel.
Improper fuel grade - Change gasoline.
Fuel system clogged - Repair or replace.
Spark plug wire is loose or disconnected - Inspect the spark plug wire connection, replace or repair.
Faulty spark plug - Replace spark plug.
Clogged fuel filter - Change fuel filter.
Defective safety switch - Replace if required.
Carburetor components worn out - Repair or replace parts.
Low engine compression - Inspect cylinder block and change defective components.
Throttle cable is damaged or adjusted incorrectly - Adjust properly or change the cable.

Unstable engine running

Cooling fins are blocked - Need to clean or wash.
Ignition system failure - Inspect ignition system and change failed components.
Choke cable is stuck or faulty - Clean or replace the cable.
Air filter element is plugged - Clean or change air filter.
Fuel pump is damaged or dirty - Inspect fuel pump and change as required.

Engine starts and stops immediately

Damaged spark plug - Change spark plug as required.
Carburetor is dirty or faulty - Service or replace carburetor.
Ignition coil is not working - Change ignition coil as required.
Valve springs are bad or broken - Change valve springs.
Valves sticking - Valves need to be cleaned.

Engine overheats

Engine oil level is insufficient - Checking oil level and add if necessary.
Engine overload - Reduce load.
Air intake screen is blocked - Need to wash or clean.
Carburetor fuel mixture is too lean - Use proper settings.
Improper ignition timing - Set the ignition timing correctly.
Valve setting is wrong - Adjust valves as required.

Engine knocking sound or abnormal noise

Stale fuel - Change gasoline.
Engine is running overloaded - Reduce load.
Engine oil level is insufficient - Check and refill engine oil.
Improperly adjusted low idle speed - Adjust idling as required.
Fuel pump is clogged or faulty - Test fuel pump and change if necessary.
Main bearings or crankshaft failure - Have bearings or crankshaft replaced.
Valve clearance is incorrect - Adjust valve clearance according to specifications.
Cylinder bore or piston rings are worn - Change defective parts.

Engine lacks power

Carburetor is dirty or incorrectly adjusted - Service or properly adjust carburetor.
Plugged air filter - Replace or clean air filter.
Fuel pump is clogged or faulty - Service or change fuel pump.
Defective ignition - Check ignition and replace faulty components.
Cylinder head gasket is damaged - Change cylinder head gasket.
Valves are burned or stuck - Clean or change valves.
Worn or defective push rod - Replace push rod.
Cylinder block parts are faulty - Replace defective components.
Plugged oil filter (if equipped) - Change or service oil filter.

Excessive fuel consumption

Throttle is not fully open - Change or adjust throttle cable.
Incorrect adjustment of carburetor main jet - Adjust main jet as required.
Defective or loose spark plug - Tighten or replace spark plug.
Valves are worn, burned or stuck - Replace or service valves.
Sleeve, rings, or piston are damaged - Replace defective components.
Incorrect valve clearance - Adjustment procedure required.

Engine consuming too much oil

Damaged gaskets or seals - Replace to repair leaks.
Worn valve stems and valve guides - Valves must be replaced.
Piston rings are stuck or worn - Replace piston rings.
Cylinder liner or piston is damaged - Check liner and piston, replace as required.
Breather pipe or hose is plugged - Service or replace.

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