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4.8 out of 5 stars. 291 reviews
A woman outside with a dog
A woman outside with a dog

SIMPSON 4,200 PSI 4 GPM Gas Cold Water Aluminum Professional Pressure Washer, Honda GX390 Engine, 49-State

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SIMPSON 4,200 PSI 4 GPM Gas Cold Water Aluminum Professional Pressure Washer, Honda GX390 Engine, 49-State

Item # 1323921

$1,499.99
or
or


Notice:
This Item cannot be shipped to CA.
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What's included
Powersport plans are not available in CA & MD.
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  • Online Only

SIMPSON 4,200 PSI 4 GPM Gas Cold Water Aluminum Professional Pressure Washer, Honda GX390 Engine, 49-State

Item # 1323921

$1,499.99
or
or
financeCard Logo
$63/mo.†  suggested payments with 24 Months Financing or earn $74 in Rewards+ on this purchase.
Valid 5/15/2026 - 7/5/2026

This item is available online only

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Notice:
This Item cannot be shipped to CA.
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What's included
Powersport plans are not available in CA & MD.
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Designed to meet the rigorous demands of the cleaning professional, the SIMPSON Aluminum 4200 PSI at 4.0 GPM HONDA GX390 with CAT Triplex Plunger Pump Cold Water Professional Gas Pressure Washer frame is crafted of aircraft grade aluminum, making it lighter in weight than most steel frame gas pressure washer designs. This gas pressure washer is perfect for contractors who specialize in deck cleaning, wood restoration, paint preparation, graffiti removal and all other professional cleaning services. The pressure washer is designed for optimum performance in the harshest environments. Get the job done right with this durable gas pressure washer!3 year limited commercial engine warranty; 5 year limited pump warranty; 10 year limited frame warranty; 90 day limited accessory warranty

For additional information on this product, please see the Product Documents section for all downloadable user manuals, installation guides, brochures and warranty statements.

Looking for more information on pressure washers? Check out our guide on how to maintain a pressure washer in the product documents section.

  • HONDA GX390 engine is equipped with a low oil shutdown feature
  • CAT PUMPS triplex pump is equipped with an integrated unloader and thermal relief valve
  • Monster hose - 3/8 in. x 50 ft. kink and abrasion resistant hose with quick connect fittings and polyurethane outer jacket
  • Aircraft grade aluminum frame is lighter in weight than most steel frame designs
  • Gas pressure washer has 13 in. premium tires for ease of maneuverability across various terrains
  • Pressure washer has 5 quick connect nozzle tips: 0, 15, 25, 40 and soap to use for a variety of cleaning applications
  • 31 in. wand lance included
  • This product is not for sale in California

Q&As

1 - 10 of 15 Questions

Q: how is this shipped

a year ago
1 Answer
  • A: The machines are shipped via Federal Express. Thanks for the question, Cleaner!
    Anonymousa year ago
    Helpful?

Q: When will this be available

2 years ago
1 Answer
  • A: Hi there, This product cannot be shipped to CA. You can contact your local store to see if they will carry this item in the future.
    2 years ago
    Helpful?

Q: Can this model pull water from a water Tank?

3 years ago
1 Answer
  • A: Hi, Ralf77. Yes, the ALH4240 will draw from a tank. Thanks for the question!
    Anonymous3 years ago
    Helpful?

Q: who manufactures the CAT Triplex Plunger Pump

4 years ago
1 Answer
  • A: CAT Pumps.
    4 years ago
    Helpful?

Q: What is the lowest psi you can adjust this model to also can it suck from a water tank ?

4 years ago
1 Answer
  • A: The minimum requirements for a water supply are 20 PSI and 5 Gallons Per Minute.
    4 years ago
    Helpful?

Q: What is the horsepower of the engine on this pressure washer?

5 years ago
1 Answer
  • A: For additional product support, please contact the manufacture.
    5 years ago
    Helpful?

Q: can the pressure be adjusted ? does it come with cleaning siphon for detergent

5 years ago
1 Answer
  • A: Please see the manual for more information: https://media.tractorsupply.com/is/content/TractorSupplyCompany/tsc/product/1/32/39/21/1323921_Man1.pdf
    5 years ago
    Helpful?

Q: Is this washer Belt Driven or Direct driven ?

6 years ago
1 Answer
  • A: It has a belt drive system.
    5 years ago
    Helpful?

Q: Does this unit have the idle down technology when it is not spraying

6 years ago
1 Answer
  • A: Sunbird, i am sorry but the ALH4240 does not have an idle down feature
    Anonymous6 years ago
    Helpful?

Q: Does this have the Honda GX 390 engine? Does this product have an automatic unloader valve so I don't have to pull the trigger to start the engine?

6 years ago
1 Answer
  • A: GHS92, This does have a Honda GX390 and all Simpson products have an unloader valve in the system which allows for the use of a trigger gun
    Anonymous6 years ago
    Helpful?
1 - 10 of 15 Questions

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Reviews

Rating Snapshot

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251 reviews with 5 stars.
29 reviews with 4 stars.
3 reviews with 3 stars.
2 reviews with 2 stars.
6 reviews with 1 star.

Overall Rating

4.8
93 out of 94 (99%) reviewers recommend this product

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Most Helpful Favorable Review

Should be the last pressure washer you ever own.

7 years ago
I had owned a 2000 PSI Honda/Cat water pump unit prior to this for 25 years. It is the best combo on the market. These units will last a generation if you never start the engine before bleeding all the air out of the system, keep the oils changed, treat the gas with preservatives, winterize the pump so water is flushed out, and keep the tires inflated with and filled with leak stop as they sit with little use. Very nice unit. The big Honda is a hard pull to start but the trick is the squeeze the spray wand trigger while trying to start to prevent the pump pressure locking. Lastly Cat pumps should not be left running with no water flow through them. The water is used to cool the pumps. If you are taking a break reach over and turn the motor switch to off to prevent pump overheating. To ease back strain with the 4200 PSI recoil drape the wand over your shoulder, the reach the trigger with the thumb of the opposite hand and squeeze the trigger this allows you to stand up without bending over greatly reducing back strain. Most owner are not aware, nor do they read the owners manual. It is evident from the review comments! The Cat pump has a black knob on it that turns the pressure way down. The owners manual misses this fact. Reduce the pressure to avoid damaging wood surfaces and for roofs use the wider nozzle to dissipate the spray pressure over a wider area. The needle nozzle is great for blowing off driveway debris in a hurry, hold the wand parallel with the ground, point and shoot.
7 people found this helpful
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Most Helpful Critical Review

Will not start

5 years ago
I pulled about 100 times and the unit would not start,I followed the instructions as directed from the manual,I have notified Simpson of this matter,as of right now I’m very displeased
3 people found this helpful
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1 to 4 of 291 Reviews .
1 – 4 of 291 Reviews
US
Review 1

POWERFUL

18 hours ago
I’ve used this to clean my deck and concrete patio. It’s REALLY powerful and does a good job cleaning. I plan to use it with a foam cannon for cleaning the cars.

Originally posted on simpsoncleaning.com

US
Review 1

BEST POWER WASHER

19 hours ago
This machine is EXCELLENT. I wash the sidings and it worked perfectly. Very powerful and removed all the dirt off thats been there for years. DEFINITELY WORTH THE MONEY.

Originally posted on simpsoncleaning.com

US
Review 1

Powerful Machine

a day ago
This machine performs excellent. Deep cleans my concrete while gently cleans my shop externally.

Originally posted on simpsoncleaning.com

Review 1

Pressure washer

a day ago
Only used it one time so far but worked as expected.

Originally posted on simpsoncleaning.com