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Home›Engines›Kohler CH18-25

Kohler CH18-25 Engine

The Kohler CH18-25 is a 2-cylinder engine. It powers generator sets from Kohler, including the CH18.

Also known as: Kohler CH18-25

Part of the Kohler CH18 engine family — 2 variants share parts & fitment.

2
Cylinders
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Engine specifications

Cylinders2

Common problems

4
  • Will Not Start
    Cause: Improper Fuel, Dirty Fuel Line/System, Grass Screen, Overloaded
    Fix: Clean or replace fuel filter; clean air cleaner element and precleaner; ensure proper battery condition.
  • MIL comes on
    Fix: If the MIL comes on, or the engine becomes hard to start, runs roughly, or stalls at low idle speed, initial checks should be made in the following areas: - Make sure the fuel tank is filled with clean, fresh gasoline.
  • Engine troubles that appear to be fuel system related
    Fix: Check the following areas before adjusting the carburetor: - Make sure the fuel tank is filled with clean, fresh gasoline. - Make sure the fuel tank cap vent is not blocked and that it is operating properly. - If the fuel tank is equipped with a shut-off valve, make sure it is open. - If the engine is equipped with an in-line fuel filter, make sure it is clean and unobstructed. Replace the filter if necessary. - Make sure fuel is reaching the carburetor. This includes checking the fuel lines and fuel pump for restrictions or faulty components, replace as necessary. - Make sure the air cleaner element is clean and all air cleaner element components are fastened securely.
  • Engine hard to start, runs roughly, or stalls at low idle speed
    Fix: If after checking the items listed above, adjust or service the carburetor. There are no accessible mixture adjustment screws on the carburetor. The only setting which can be changed is the low idle speed. 1. Start the engine and run at half throttle for 5 to 10 minutes to warm up. The engine must be warm before making final settings (steps 2 and 3). 2. Low idle Speed Setting: Place the throttle control into the “idle” or “slow” position. Set the low idle speed to 7200 RPM (+ 75 RPM) by turning the low idle speed adjusting screw in or out. Check the speed using a tachometer. *NOTE: The actual low idle speed depends on the application - refer to equipment manufacturers recommendations. The standard low idle speed is 1200 RPM. 3. If proper operation is not restored after adjusting the low idle speed, carburetor servicing by an authorized Kohler Engine Service Dealer may be required.

Compiled from service & troubleshooting documentation across every generator set that uses the Kohler CH18-25.

Maintenance schedule

ItemSpecCapacityPart #Interval
Air filterService air cleaner element. Replace heavy-duty air cleaner element and check inner element.—500 hr
Fuel filterEFI Engines: A special, high volume, high pressure filter with greater filtration capabilities and internal surface area is used. See Figure 15.—
Oil filterChange oil filter. Replace fuel filter (EFI engines).—200 hr
BatteryBattery Charging: WARNING: Explosive Gas! Batteries produce explosive hydrogen gas while being charged. To prevent a fire or explosion, charge batteries only in well ventilated areas. Keep sparks, open flames, and other sources of ignition away from the battery at all times. Keep batteries out of the reach of children. Remove all jewelry when servicing batteries.—
BeltHave Bendix starter drive serviced. Have solenoid shift starter disassembled and cleaned.—500 hr
CoolantCheck oil cooler fins, clean as necessary (if equipped).—250 hr
OilChange oil after every 100 hours of operation (more frequently under severe conditions). Refill with service class SG, SH, SJ or higher oil as specified in the “Viscosity Grades” table (Figure 3) on page 5.—100 hr
Spark plugCheck spark plug condition and gap.—250 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Parts cataloged across the Kohler CH18 family

7
Part #DescriptionCategory
25 755 20-SAir cleaner cleanout kit (black)air_filter
25 083 04-SInner Element, Heavy-Duty Air Cleanerinner_element
24 083 02-4Oil Cooler, CH25oil_cooler
24 083 05-4Oil Cooler, CH26oil_cooler
25 083 01-SOuter Element, Heavy-Duty Air Cleanerouter_element
24 083 03-4Paper Element, Heavy-Duty Air Cleanerpaper_element
KO3226Starter Service Kitstarter

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Aftermarket parts that fit this engine

2
4585301 FridayParts $32.35 4585309 FridayParts $24.00

Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.

Common questions

Which generators use the Kohler CH18-25 engine?

The Kohler CH18-25 powers 1 generator set(s), including Kohler CH18.

How often should you change the oil in the Kohler CH18-25?

The Kohler CH18-25 oil change interval is every 100 hours.

What is a common problem with the Kohler CH18-25 engine?

A commonly reported issue on generators using the Kohler CH18-25 is: Will Not Start. Cause: Improper Fuel, Dirty Fuel Line/System, Grass Screen, Overloaded. Fix: Clean or replace fuel filter; clean air cleaner element and precleaner; ensure proper battery condition..