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Kohler CV16S Engine - Nikki Carburetor

Kohler CV16S - Nikki Carburetor Adjustment

Kohler CV16S engines are equipped with fixed main jet Nikki carburetors. Nikki carburetors only have a low idle speed screw. Carburetors will have fixed idle fuel or a limiter cap on the idle fuel adjusting needle.

Carburetor adjustments should be made only after the engine has warmed up. The carburetor is designed to deliver the correct fuel to air mixture to the engine under all operating conditions. The main fuel jet is calibrated at the factory and is not adjustable.

The idle fuel adjusting needle is also set at the factory and normally does not need adjustment. Engines operating at altitudes above approximately 1830 m (6000 ft.) may require a special high altitude main jet. If, however, the engine is hard-starting or does not operate properly, it may be necessary to adjust or service the carburetor.

Low Idle Speed Setting

1) Start the engine and run at half throttle for 5 to 10 minutes to warm up. The engine must be warm before doing step 2.

2) Low Idle Speed Setting: Place the throttle control into the idle or slow position. Set the low idle speed to 1200 RPM (±75 RPM) by turning the low idle speed adjusting screw in or out. Check the speed using a tachometer. The actual low idle speed depends on the application refer to equipment manufacturer's recommendations. The recommended low idle speed for basic engines is 1200 RPM. To ensure best results when setting the low idle fuel needle, the low idle speed must not exceed 1200 RPM (±75 RPM).

Kohler CV16S - Nikki Carburetor Disassembly

- Remove the bowl retaining screw, retaining screw gasket, and fuel bowl.
- Remove the bowl gasket, float shaft, float, and fuel inlet needle.
- Remove the low idle speed screw and spring.
- If there is a low fuel adjusting needle without a limiter cap, remove the needle and spring.
- Do not attempt to remove the needle if it has a limiter cap.
- Further disassembly to remove the welch plugs, main fuel jet, fuel inlet seat, throttle plate and shaft, and choke plate and shaft is recommended only if these parts are to be cleaned or replaced.

Main Fuel Jet Removal

The main jet on Nikki carburetors is threaded into the tip of the fuel shut-off solenoid. It can be removed for inspection or cleaning.

Fuel Inlet Seat Removal

The fuel inlet seat is pressed into the carburetor body, do not attempt to remove it. If necessary, clean it in place with aerosol carburetor cleaner.

Choke Shaft Removal (Self-Relieving)

The self-relieving choke used on some carburetors. Use the following procedure to replace the self-relieving choke components using Choke Repair Kit. Remove the black dust cover. This cover snaps on and off. Remove and discard the two screws fastening the choke plate to the choke shaft. Remove and discard the choke plate and choke shaft from the carburetor.

Remove the upper brass bushing using one of the following procedures: Use a slide hammer type bearing puller. Use a screw extractor (for 5/32 dia. hole). Secure extractor in a vise. Turn carburetor on to the extractor. While pulling on the carburetor, lightly tap the carburetor casting with a hammer or use a size 12-28 tap if a screw extractor is not available.

Kohler CV16S - Nikki Carburetor Cleaning

- Carburetor body and bore; especially the areas where the throttle plate, choke plate and shafts are seated.
- Idle fuel and idle ports in carburetor bore, main jet, bowl vent, and fuel inlet needle and seat.
- Float and float hinge. Fuel bowl.
- Throttle plate, choke plate, throttle shaft, and choke shaft.
- Do not submerge the carburetor in cleaner or solvent when fiber, rubber, or foam seals or gaskets are installed.
- The cleaner may damage these components.

Kohler CV16S - Nikki Carburetor Reassembly

Choke Shaft Installation (Self-Relieving)

Before installing kit parts, thoroughly clean the carburetor body with compressed air. Install the new bushing through the new lever and align the slot in the bottom of the lever over the lever stop pin. To ensure the proper alignment of the upper bushing and the lower shaft hole use a 3/16 diameter drill blank to align the bushing as it is pressed into the casting.

Install choke shaft and spring assembly with the lower spring tang installed in the second notch from the right. Loosely attach the choke plate to the choke shaft using the two screws provided in the choke repair kit. Apply Loctite to the threads of the choke plate retaining screws.

Secure these screws only after the choke plate is properly aligned in the choke bore. To align choke plate, insert a 0.010 in. shim between the top right edge of the choke plate and bore. Then while pushing down on the top of the choke shaft, tighten screws securely.

Check choke shaft and choke plate for freedom of movement by performing the following: Using the choke lever, close the choke plate. The choke lever and choke plate should move in unison. While holding the choke lever in the closed position, push on the long side of the choke plate. The choke plate should open and spring closed freely.

While holding the choke lever in the wide open position, the choke plate should be against the wide open choke plate stop pin. Install new dust cover by pushing it down until it snaps into place. After the carburetor is reinstalled on the engine, recheck choke system for freedom of movement by moving the wire link in the direction to close the choke and releasing it. The link should move freely in both directions.

High Altitude Operation

When operating the engine at altitudes of 1830 m (6000 ft.) and above, the main fuel mixture tends to get overrich. An overrich mixture can cause conditions such as black, sooty exhaust smoke, misfiring, loss of speed and power, poor fuel economy, and poor or slow governor response.

To compensate for the effects of high altitude, a special high altitude main fuel jet can be installed. High altitude jets are sold in kits which include the jet and necessary gaskets. Refer to the Parts Manual for the engine being serviced for the correct kit number.