Kohler PA-CH680-3171 22.5HP Command PRO Horizontal Engine for Walker ZTR Mowers

Current Kohler replacement engine for multiple discontinued Walker CH20S, CH640, CH641, and CH680 engine specifications.

Verified Kohler Replacement Numbers

The current PA-CH680-3171 engine replaces or supersedes the following Kohler Walker engine specification and part numbers:

The “PA-” prefix may appear on packaging, invoices, dealer systems, and engine listings. The engine identification label may show the model and specification without the PA prefix.

Factory Inventory: As of July 16, 2026, Kohler's dealer inventory system reports approximately 113 engines available. Inventory changes daily and is not guaranteed until your order is accepted and scheduled for shipment. 

Historical Replacement Progression

Depending on the age of the Walker mower, the original engine may have passed through more than one Kohler replacement number before reaching the current PA-CH680-3171 configuration. A typical replacement progression may appear as follows:

The precise sequence can vary by the original engine specification. The important issue is whether the complete engine specification number is included in Kohler's replacement group. Do not select a replacement engine based only on horsepower or the general CH20, CH640, CH641, or CH680 model family.

PA-CH680-3171 Current Engine Information

Horsepower descriptions on older listings may show 20HP, 20.5HP, 22.5HP, or 23HP. The complete Kohler model and specification number is more important than the historical horsepower description.

Why the Horsepower Number Changed

Some of the original Walker engines were marketed as 20HP or 20.5HP engines, while later CH680 versions were marketed as 22.5HP or 23HP. This does not necessarily mean the replacement is incorrect.

Kohler changed engine families, displacement, rating standards, emissions configurations, and production specifications over time. Replacement compatibility is determined by the complete Kohler specification and supersession history—not by matching the advertised horsepower number alone.

Command PRO Engine Features

• Commercial-duty overhead-valve V-twin design
• 674cc displacement
• Cast-iron cylinder liners
• Hydraulic valve lifters
• Electronic ignition
• Automatic Compression Release for easier starting
• 12-volt electric starter
• 15-amp charging system
• Full-pressure lubrication system
• Spin-on, full-flow oil filter
• Integrated oil-cooling features
• Hardened crankshaft journals
• Heavy-duty air-filtration system
• High-efficiency cooling fan
• Fuel-shutdown solenoid
• Mechanical governor
• Replaceable in-line fuel filter

Walker Mower Application

PA-CH680-3171 is designed for applicable Walker zero-turn-radius mower installations originally equipped with one of the supported engine specification numbers listed on this page.

Walker may use application-specific components that are not automatically included with a replacement engine. Depending on the mower model and original engine, installation may require transferring or reusing some of the following:

• Muffler and exhaust pipes
• Exhaust mounting brackets
• Air-cleaner housing or intake components
• Throttle and choke cables
• Control brackets
• Electrical connectors or wiring adapters
• Fuel lines and fittings
• Pulleys, clutches, couplings, or driven components
• Heat shields
• Mounting hardware
• Other Walker-specific components

The current replacement engine may not look exactly like the original engine being removed. Differences in covers, labels, wiring, controls, air-filter components, and other production details do not automatically indicate that the replacement engine is incorrect.

What You Receive

• One genuine Kohler PA-CH680-3171 Command PRO engine
• Factory-installed components supplied as part of Kohler's current CH680-3171 configuration
• Engine manual when included by Kohler
• Kohler factory warranty documentation when supplied by the manufacturer

Not automatically included: fuel tank, muffler, exhaust system, clutch, pulley, wiring adapter, throttle cable, choke cable, equipment-specific mounting brackets, heat shields, fuel lines, installation labor, or other Walker-specific components unless expressly stated as included.

Verification Before Ordering

Before placing the order, locate the Kohler identification label on the original engine. The label normally provides the complete engine model, specification, and serial number.

For the most accurate verification, email clear photographs of:

• The complete Kohler engine identification label
• The entire engine installation
• The PTO, crankshaft, or driven end of the engine
• The engine wiring connector and electrical connections
• The air-cleaner and intake arrangement
• The muffler and exhaust arrangement
• The throttle and choke control connections
• The Walker mower model and serial-number label

Frequently Asked Questions

Does PA-CH680-3171 replace PA-CH680-3057?
Yes. PA-CH680-3171 is the current replacement for PA-CH680-3057.

Does it replace PA-CH680-3127?
Yes. PA-CH680-3127 has been superseded by PA-CH680-3171.

Does it replace CH680-3024?
CH680-3024 is included in the older Walker CH680 replacement group that progressed through later specifications, including CH680-3057, before PA-CH680-3171.

Does it replace CH641-3013?
Yes. PA-CH641-3013 is shown as replaced by PA-CH680-3171.

Does it replace CH641-3012?
CH641-3012 is listed among the older Walker engine specifications superseded by CH680-3171.

Does it replace CH640-3013?
Yes. CH640-3013 is listed as an older Walker engine that can be replaced by CH680-3171.

Does it replace CH640-3109?
CH640-3109 is listed in the supersession group for the current CH680-3171 Walker engine. Because it is an older engine configuration, verify the installation and determine which original Walker components must be transferred.

Does it replace CH20S-64757?
Yes. CH20S-64757, also displayed in some systems as PA-64757, is an older Walker engine specification superseded by the current CH680-3171.

Does it replace CH20S-64694?
CH20S-64694, also displayed as PA-64694, is listed among the older Walker engine numbers superseded by PA-CH680-3171.

Why does my original engine say 20HP?
The original engine may have been sold under an older horsepower rating. Kohler later consolidated several older Walker specifications into a newer 674cc CH680 replacement. Order by the complete specification number rather than horsepower alone.

Will the new engine look exactly like my original?
Not necessarily. Replacement engines can have different covers, labels, controls, filters, electrical connectors, or other production details. Some original Walker-specific components may need to be reused.

Does the engine include a muffler?
No muffler should be assumed to be included unless the quotation or product options specifically state that one is included.

Is the fuel tank included?
No. The mower normally supplies the fuel tank and related equipment-specific fuel system.

Is this a universal 22.5HP replacement engine?
No. PA-CH680-3171 is a Walker-specific engine configuration. Other CH680 engines can have different crankshafts, controls, wiring, charging systems, mounting arrangements, and equipment applications.

Is professional installation recommended?
Yes. Engine replacement should be performed by a qualified small-engine or Walker mower technician familiar with engine alignment, wiring, fuel systems, exhaust installation, controls, and rotating equipment.

Special-Order Engine Policy

The customer and installer are responsible for confirming engine compatibility before installation. Do not add fuel or oil, modify the engine, install a clutch or pulley, alter the wiring, or begin installation until the model, specification, shaft configuration, mounting arrangement, and supplied components have been inspected and confirmed.

Warranty Information

Warranty coverage is provided by Kohler under the applicable Kohler engine warranty. Warranty terms, coverage periods, exclusions, and procedures are controlled by Kohler and may vary by engine application and end use.

Factory engine warranties generally cover qualifying defective engine parts. They do not automatically cover removal, installation, diagnosis, travel, downtime, loss of use, equipment modifications, freight, or unrelated mower components. Contact an authorized Kohler service center for warranty diagnosis and authorization before performing warranty repairs.

Product and Image Disclaimer

Product photographs are for general reference only. Kohler may change engine colors, labels, covers, controls, wiring, filters, brackets, hardware, and other production details without notice. Always order by the current Kohler part number and verified replacement information, not by product appearance alone.

Specifications, dimensions, horsepower descriptions, replacement relationships, included components, availability, warranty terms, emissions compliance, and pricing are subject to manufacturer revision without notice. When a particular feature or dimension is critical, request written verification before ordering.

Kohler, Command PRO, Walker, and related model names are trademarks of their respective owners. Steam-Brite is an independent equipment dealer and uses manufacturer names and part numbers solely for product identification and replacement reference.