Kohler 20 853 35-S Carburetor | Riding Mower Repair Guide

The Kohler 20 853 35-S carburetor serves Courage single-cylinder and some Command series engines on riding mowers, zero-turns and utility vehicles. This Nikki-type carburetor features auto-choke on many models, making diagnosis different from manual-choke setups. This guide covers common problems and complete repair procedures.

Table of Contents

• Engine Applications
• Part Number Cross-Reference
• Auto-Choke System
• Failure Symptoms
• Replacement Procedure
• Rebuild Guide
• Adjustments

Engine Applications

The 20 853 35-S fits Kohler Courage and some Command engines.

Courage Single-Cylinder:

• SV470 (15HP)
• SV480 (16HP)
• SV530 (17HP)
• SV540 (18HP)
• SV590 (19HP)
• SV600 (20HP)

Equipment Using These Engines:

• Husqvarna YTH series
• Cub Cadet LT, XT series
• Troy-Bilt Bronco, Pony
• Craftsman riding tractors
• Toro TimeCutter zero-turns
• MTD and Yard Machines tractors

[NEED REAL IMAGE: Kohler Courage engine model number location]

Finding Engine Model: Look for the silver Kohler spec decal on the engine shroud. It shows the model (SV540), spec number and serial number.

Part Number Cross-Reference

Kohler has superseded several carb numbers to the 20 853 35-S.

Part Number	Status
20 853 35-S	Current
20 853 33-S	Superseded
20 853 16-S	Older, replaced
20 853 44-S	Similar, verify fit
20 853 45-S	Auto-choke variant

Important: Some numbers have different choke systems. Verify your engine’s choke type before ordering.

Price Range:

• Genuine Kohler: $75-120
• Aftermarket: $25-50

Auto-Choke System

Many Courage engines use an automatic choke that causes confusion during troubleshooting.

How Auto-Choke Works

1. Cold engine: A bi-metal thermostat holds choke closed
2. Engine starts: Heat from engine warms thermostat
3. Warming up: Thermostat gradually opens choke
4. Full operating temp: Choke fully open

Auto-Choke Problems

Choke stays closed (engine floods):

• Thermostat failed
• Linkage binding
• Thermostat not reaching heat

Choke stays open (hard cold start):

• Thermostat failed
• Choke butterfly stuck
• Linkage disconnected

Testing Auto-Choke

1. With cold engine, verify choke plate is closed
2. Start engine and watch choke
3. Should begin opening within 2-3 minutes
4. Fully open within 5-7 minutes

If choke doesn’t move: thermostat likely failed. Replacement thermostat is around $30-50.

[NEED REAL IMAGE: Kohler auto-choke thermostat location and linkage]

Failure Symptoms

No Start - Cranks But Won’t Fire

Check in order:

1. Fuel reaching carburetor (loosen fuel line at carb, should flow)
2. Spark at plug (ground plug against engine, crank)
3. Choke operation (should be closed when cold)
4. Anti-afterfire solenoid clicking (if equipped)

Carburetor causes:

• Jets clogged from old fuel
• Anti-afterfire solenoid failed (stuck closed)
• Float needle stuck shut

Starts Then Dies

Fires briefly then quits. Maybe runs 5-10 seconds.

Causes:

• Main jet partially clogged
• Fuel delivery problem
• Anti-afterfire solenoid not staying energized

Backfires Through Exhaust on Shutdown

Loud pop when you turn key off.

Cause: Failed anti-afterfire solenoid. It’s not cutting fuel when engine stops.

Surging - RPM Hunts Up and Down

Classic governor hunting symptom.

Carburetor causes:

• Lean mixture (restricted fuel delivery)
• Air leak at carb gasket
• Fuel filter clogged

Non-carb causes:

• Governor linkage binding
• Governor shaft worn (check for play)

Black Smoke - Runs Rich

Engine smokes, fouls plugs, uses excessive fuel.

Causes:

• Choke stuck partially closed (auto-choke failure)
• Float stuck or sunk
• Inlet needle leaking
• High-speed mixture too rich

Fuel Leaking From Carburetor

Gas dripping from carb body.

Causes:

• Float needle not seating
• Bowl gasket failed
• Primer bulb cracked (if equipped)

Replacement Procedure

Allow 45-60 minutes for complete replacement.

Tools Required

• Socket set (3/8” and 1/2”)
• Screwdriver set
• Needle-nose pliers
• 10mm and 13mm wrenches
• Fuel line clamp
• Shop rags
• Drain pan

Step-by-Step

1. Disconnect battery

Negative cable first. Prevents sparks and accidental cranking.

2. Locate and photograph everything

Take multiple photos of all linkages, hoses and wiring before touching anything.

3. Remove engine shroud/covers

Access may require removing plastic covers or shroud sections.

4. Close fuel valve

Under the fuel tank. If no valve, clamp the fuel line.

[NEED REAL IMAGE: Kohler Courage carburetor access on riding mower]

5. Disconnect fuel line

At the carburetor inlet. Have drain pan ready.

6. Disconnect solenoid wire

If equipped, unplug the anti-afterfire solenoid connector.

7. Disconnect throttle and choke linkages

Multiple rods and springs. Match to your photos during reassembly.

8. Remove air filter base

Usually 2-3 bolts. Provides access to carb mounting.

9. Remove carburetor mounting nuts

Two nuts on studs. Support carb while removing.

10. Pull carburetor off

Note intake gasket position.

11. Transfer components if needed

Some parts like the fuel shut-off solenoid may need to swap to new carb.

12. Install new carburetor

New gaskets, slide onto studs, hand-start nuts.

13. Reconnect all linkages per photos

Take your time. Wrong positions cause problems.

14. Reconnect fuel line and solenoid

15. Open fuel valve, check for leaks

Watch for drips before starting.

16. Reconnect battery and test

Should start within a few cranks.

Rebuild Guide

Rebuilding saves money when the carb isn’t corroded.

Rebuild Kit Contents

Kohler kit 20 757 01-S (or similar):

• Bowl gasket
• Inlet needle and seat
• Float (sometimes)
• Mixture screw o-rings
• Various gaskets

Cost: $20-35

Disassembly

1. Remove bowl

Four screws or a single bolt depending on version.

2. Remove anti-afterfire solenoid

Unscrew from bowl area. Test it (see testing section below).

3. Remove float and needle

Push out hinge pin. Lift float and needle together.

4. Remove main jet

Center of emulsion tube tower. Flathead screwdriver.

5. Remove mixture screw

Count turns before removal. Typically 1.5-2 turns out.

Cleaning

Soak all metal parts in carburetor cleaner. Minimum one hour.

Clear every passage with carb spray and compressed air:

• Main jet (hold to light - should see through)
• Idle passages (tiny holes around throttle plate)
• Bowl drain/solenoid passage
• Fuel inlet passage

Inspect emulsion tube - clear all small holes.

Reassembly

Use all new gaskets from kit.

Float height: With carb inverted, float should be approximately parallel to the body. Some specs call for 0.940” to 1.000” from gasket surface to float bottom.

Mixture screw: Return to counted position or factory spec (typically 1.5 turns out).

Adjustments

Anti-Afterfire Solenoid Testing

Testing:

1. Remove solenoid from carburetor
2. Apply 12V to terminal (positive) and body (ground)
3. Plunger should retract with power
4. Plunger should extend when power removed
5. Listen for click

No click/movement = failed solenoid. Replace it ($25-40).

Mixture Screw Adjustment

If equipped with adjustable mixture:

1. Start engine, warm up 5 minutes
2. Set to idle
3. Turn mixture screw clockwise until engine stumbles
4. Turn counterclockwise until stumbles
5. Set midway, favoring slightly rich

Governor Static Adjustment

After carb work, verify governor setting:

1. Loosen governor arm clamp bolt
2. Rotate governor shaft clockwise (looking from above)
3. Move throttle lever to wide open
4. Tighten clamp bolt
5. Check no-load RPM: typically 3400-3600

Choke Adjustment

Manual choke: Should close completely when engaged, open completely when released.

Auto-choke: Verify thermostat positions choke correctly. If not, replace thermostat.

Common Issues After Repair

Engine Starts But Races

Governor linkage connected wrong. Recheck against photos.

Engine Won’t Stay Running

Solenoid wire not connected or solenoid failed.

Backfires When Starting

Usually timing related (sheared flywheel key) rather than carburetor. Check if this started after hitting something.

Runs Rough at Idle Only

Idle circuit still partially clogged. Clean more thoroughly or replace carburetor.

Frequently Asked Questions

Genuine Kohler vs aftermarket - worth the price difference?

For mowers you’ll keep, genuine Kohler carbs last longer and fit better. Aftermarket works for budget repairs or older equipment.

Can I eliminate the anti-afterfire solenoid?

You can plug the hole and run without it. The engine will backfire on shutdown but run otherwise. Not recommended as a permanent solution.

Why does my auto-choke engine flood when cold?

Auto-choke thermostat failed in the closed position. Replace thermostat.

The carb looks fine but engine still surges.

Could be governor issue (worn shaft or binding linkage) rather than carburetor. Check for play in governor shaft.

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Kohler Courage carburetors are reliable but suffer from the same ethanol fuel problems as everything else. Use stabilized fuel, service annually and these engines run for decades.