DUROMAX XP18HPX User manual

This manual provides information regarding the
operation and maintenance of these products. We
have made every effort to ensure the accuracy of the
information in this manual. We reserve the right to
change this product at any time without prior notice.
5800 Ontario Mills Pkwy
Ontario, CA 91764 USA
www.duromaxpower.com
Call our Customer Care Team Toll Free 8-5 pm PST Mon-Fri
844-DUROMAX
REV: XP18HPX_rev04082022
XP18HPX
USER MANUAL

CONTENTS
1. Introduction .................................................................................................................... 6
General Safety Procedures............................................................................................ 8
Unit and Purchase Information................................................................................... 12
Engine Components ..................................................................................................... 13
Package Contents ......................................................................................................... 14
Introduction
4.
Maintenance Schedule................................................................................................. 34
Break-In Period ............................................................................................................. 35
Maintenance Log........................................................................................................... 35
Checking the Oil ............................................................................................................ 36
Changing the Oil............................................................................................................ 37
Changing the Air Filter.................................................................................................. 38
Spark Plug Maintenance .............................................................................................. 40
Removing the Propane Hose....................................................................................... 42
Emptying the Gas Tank ................................................................................................ 44
Storing the Engine for Same Day Use ........................................................................ 46
Storing the Engine for Use Within 30 Days................................................................ 47
Storing the Engine for Longer Than 30 Days............................................................. 48
Maintenance and Care
3.
Check the Oil ................................................................................................................. 22
Check the Gas Level...................................................................................................... 23
Starting the Engine Using Gasoline............................................................................. 24
Starting the Engine Using Propane............................................................................. 26
Starting the Engine Using the Recoil Start ................................................................. 30
Starting the Engine
2.
Adding Oil ...................................................................................................................... 17
Connect the Battery...................................................................................................... 18
Adding Gasoline ............................................................................................................ 19
High Altitude Operation ............................................................................................... 20
Engine Setup

CONTENTS
7. .......................................................................................................................... 64
Warranty
8. ......................................................................................................... 68
Customer Service
6. Troubleshooting
...........................................................................................................61
5. Specications................................................................................................................. 53
Adjustment, Torque, and Timing Specications ....................................................... 54
Engine Diagrams........................................................................................................... 55
Wiring Diagram ............................................................................................................. 57
Specications

5
...........................................................................................................61

6
THE DUROMAX WAY
The DuroMax Way is more than just a brand, it is our understanding and appreciation of just how
important power can be to someone without it…
DUROMAX FOR HOME
Electricity in our home not
only provides comfort but
safety as well. From keeping
the heat or A/C on to keeping
our food cold, power is
essential to our daily lives.
Inevitability when disaster
strikes and we are left without
power for a prolonged period
of time, our way of life is
put at risk. This is by far the
most critical time for reliable
portable power.
DUROMAX FOR WORK
On the job site, portable
power allows you the ability
to get work done in remote
locations when traditional
power sources are usually
unavailable. Equipment like
table saws, sanders, and
work lights are a necessity
and portable power can
play a critical role in getting
a job done successfully and
eciently.
DUROMAX FOR PLAY
Camping outdoors in a
remote location can get one
in touch with nature and allow
them to forget the stress of
the day to day grind. Here
portable power can provide
comfort as well as safety. With
portable power, you can keep
your cell phone charged, light
up your campsite, or even
brew a cup of coee, all while
being miles from civilization.
The DuroMax Way is a commitment to excellence. This vision is focused on the quality, reliability,
and durability of our products combined with outstanding customer service. We understand that
having dependable power whenever and wherever you need it provides comfort, safety, and peace
of mind. It is through this philosophy that DuroMax achieves our vision of...

7
INTRODUCTION
DuroMax Power Equipment is headquartered in Ontario, California and is the industry’s leader in
Dual Fuel portable generator technology. In addition to a full assortment of portable generators
ranging from digital inverters to large 15,000-watt portable standby units, their product line
includes pressure washers, engines, pumps, and accessories.
The foundation of our company is built on quality, reliability, durability, and customer service. At
DuroMax our vision is simple, we are committed to Powering Everyone... Anywhere!
STOP
Please do not return
to the store.
DuroMax representatives are ready to help you
with any questions, concerns, or issues about your
new product. We can guide you through assembly,
start up, and how to operate your new generator.
We want you to be able to put your new generator
to use right away!
CALL US BEFORE YOU CONSIDER
RETURNING THE PRODUCT!
1-844-DUROMAX
TOLL-FREE
Engines that are certied to comply with U.S. EPA emission regulations for SORE (Small o Road
Equipment), are certied to operate on regular unleaded gasoline and may include the following
emission control systems: (EM) Engine Modications and (TWC) Three-Way Catalyst (if so equipped).
Notice Regarding Emissions

88
DANGER:This engine produces poisonous carbon monoxide gas when running. This gas
is both odorless and colorless. Even if you do not see or smell gas, carbon monoxide may
still be present. Breathing this poison can lead to headaches, dizziness, drowsiness, and
eventually death.
●Use outdoors ONLY in non-conned areas.
●Keep several feet of clearance on all sides to allow proper ventilation of the engine.
WARNING: The exhaust from this product contains chemicals known to the State of
California to cause cancer, birth defects, or other reproductive harm.
WARNING: This engine produces heat when running. Temperatures near exhaust can
exceed 150°F (65°C).
●Do not touch hot surfaces. Pay attention to warning labels on the engine denoting hot
parts of the machine.
●Allow engine to cool several minutes after use before touching engine or areas which
heat during use.
GENERAL SAFETY PROCEDURES
Please familiarize yourself with the following safety symbols and words:
●DANGER: Indicates a hazard that will result in serious injury or death if instructions are not
followed.
●WARNING: Indicates a strong possibility of causing serious injury or death if instructions are not
followed.
●CAUTION: Indicates a possibility of personal injury or equipment damage if instructions are not
followed.
SAFETY ALERT SYMBOL
The safety alert symbol is used with one of the safety words (DANGER,
WARNING, or CAUTION) to alert you of hazards. Please pay attention to
these hazard notices both in this manual and on the engine.

9
WARNING: This engine may emit highly ammable and explosive gasoline vapors, which
can cause severe burns or even death. A nearby open ame can lead to an explosion
even if not directly in contact with gasoline.
●Do not operate near an open ame.
●Do not smoke near the engine.
●Always operate on a rm, level surface.
●Always turn the engine o before refueling.
●Allow engine to cool for at least 2 minutes before removing the fuel cap. Loosen cap
slowly to relieve pressure in the tank.
●Do not overll the gas tank. Gas may expand during operation. Do not ll to the top
of the tank.
●Always check for spilled gas before operating.
●Empty the gasoline tank before storing or transporting the engine.
●Before transporting, turn the fuel valve to the o position and disconnect
the spark plug.

10
In addition to the above safety notices, please familiarize
yourself with the safety and hazard markings on the
engine.
GENERAL SAFETY PROCEDURES (CONTINUED)

DON’T TOUCH
CAUTION HIGH TEMPERATURE
DANGER HOT EXHAUST
KEEP SAFE DISTANCE
DON’T TOUCH
BURN RISK CARBON MONOXIDE SAFE DISTANCE
11

Serial Number
Serial number format
STAPLE RECEIPT HERE
The serial number will be shown in two parts. The engine
model, followed by the serial number.
Engine Model: _____________________________________________
Serial Number: _____________________________________________
A purchase receipt may be necessary for warranty parts or
service in the future. If you have a paper receipt staple it
here for easy reference.
If you purchased the unit online, save the email receipt
where you can access it, and record your details here for
convenience in the future.
Purchase Date: ____________________________________________
Order Number: ____________________________________________
Retailer Name: _____________________________________________
Serial number
The serial number is located on the engine block, to the left of
the oil ll.
UNIT AND PURCHASE INFORMATION
12

1. Propane Regulator - A propane regulator with included hose that easily installs on a propane
tank.
2. Air Filter - A removable, cleanable, oiled, element that cleans the air going into the engine.
3. Carburetor - A component used to control the air fuel mixture of the engine.
4. Fuel Tank - All metal 1.4 gallon gasoline fuel tank.
5. Recoil Starter - An easy pull recoil start to start the engine without the electric start.
6. Key Switch Box - An electric start switch that engages the starter motor with the turn of a key.
7. Recoil Handle - An easy grip handle used to pull the recoil starter rope.
8. Starter Motor - Electric motor that starts the generator electrically for easy starting.
9. Muer - A noise dampening component that helps lower the engine decibel level.
10. Engine Shaft - A 1” diameter, 2-3/4” long all metal shaft with a 1/4” keyway.
11. Oil Fill - An easy access location to ll the oil for the engine.
12. Oil Drain Plug - An easy to remove oil plug that is used to drain the oil.
ENGINE COMPONENTS
4. Fuel Tank
13
8. Starter Motor 9. Muer
10. Engine Shaft
11. Oil Fill
5. Recoil Starter
6. Key Switch Box
3. Carburetor
2. Air Filter
12. Oil Drain Plug
7. Recoil Handle
1. Propane Regulator

PACKAGE CONTENTS
Your engine comes with the items listed below. Please check to see that all of the following items
are included with your engine.
●Note: Actual tools may dier in appearance or design from image shown.
Spark Plug Wrench Oil Funnel Engine Keys
Used in spark plug
maintenance, inspection, and
installation.
Used to add oil to the engine
without messy spills.
Used to start the engine.
Battery Leads
Used to hook up a 12V battery
to the starter motor.
14

ENGINE SETUP
Proper setup of your engine will get you going as soon as possible while making sure you and your
equipment are safe and cared for.
15

16

Add oil
The engine requires engine oil to operate properly. The engine, when new from the package
contains no oil in the crankcase*. You must add the proper amount of oil before operating the
engine for the rst time. This amount is equal to the oil capacity of the engine crankcase:
a. Make sure the engine is on a level surface.
b. Unscrew the oil ller cap from the engine .
c. Using a funnel, add the appropriate amount of oil
into the crankcase. You can check the oil level of the
engine with the dipstick located below the oil
ller cap. Simply pull the dipstick out and the
indicated oil level is on the end of the stick.
d. Replace oil ller cap.
1.
Step 1- Adding Oil
Model Number XP18HPX
Engine Oil Capacity 37.2 . oz (1.1L)
WARNING: DO NOT overll the crankcase. This
may damage the motor and shorting overall life
of your engine.
WARNING:Do not apply engine oils with additives or 2-stroke gasoline engine oils;
they don’t have enough lubrication and may shorten the engine’s service life.
Engine oil recommended: SAE 10W-30.
Viscosity varies with regions and temperatures. Choose your
oil viscosity using the chart to the left.
* A small amount of oil from factory testing may be present on
arrival.
* Synthetic oil may be used after the 8 hour initial break-in
period. Using synthetic oil does not increase the recommended
oil change interval. Full synthetic 5W-30 oil will aid in starting in
cold temperatures <5ºC (41ºF).
ENGINE SETUP
17

Step 2 - Connect the Battery
18
ENGINE SETUP (CONTINUED)
Connect positive battery lead
1.
Connect negative battery lead
2.
a. Remove the outer nut of the starter solenoid and
slide the ring terminal end of the red positive lead
over the outer solenoid bolt.
a. Connect the ring terminal end of the black negative
battery lead to any bolt location on the non-painted
metal engine casting.
Connect both leads to battery.
3.
a. First slide the positive battery terminal clamp lead
end to a 12V battery positive terminal and tighten
the battery terminal clamp.
b. Reinstall outer nut on starter solenoid outer bolt.
b. Then take the negative battery terminal clamp lead
end to a 12V battery positive terminal and tighten
the battery terminal clamp.

Step 3 - Adding Gasoline (Optional)
Add gasoline
a. Make sure the engine is on a level surface.
b. Unscrew gas cap and set aside (NOTE: the gas cap
may be tight and hard to unscrew).
c. Slowly add unleaded gasoline to the fuel tank. Be
careful not to overll.
d. Replace fuel cap and wipe up any spilled gasoline
with a dry cloth.
DANGER
DO NOT OVERFILL
THE GAS TANK
OVERFILLING CAN RESULT
IN A FIRE, EXPLOSION,
OR DEATH.
1.5”
IMPORTANT:
●To ensure that the engine runs smoothly use only FRESH, UNLEADED GAS WITH AN
OCTANE RATING OF 87 OR HIGHER.
●Never use an oil/gasoline mixture. Never use old gas.
●Avoid getting dirt or water in the fuel tank.
●Gas can age in the tank and make it hard to start up the engine in the future.
●Never store engine for extended periods of time with fuel in the tank.
WARNING: Gas can expand. Do not ll the gas tank to the very top. Leave a
minimum of 1.5 in open space. Gasoline and gas fumes are highly ammable.
Do not ll the tank near an open ame. Always check for fuel spills.
Model Number XP18HPX
Gas Tank Capacity 1.4 US gal. (5.325 L)
19

20
High Altitude Operation
At high altitudes, the standard carburetor air/fuel mixture will be too rich. The performance will decrease,
and fuel consumption will increase. A very rich mixture will also foul the spark plug and cause hard starting.
Operation at an altitude that diers from that at which this engine was certied, for extended periods of
time, may increase emissions. High altitude performance can be improved by specic modications to
the carburetor. If you always operate your engine at altitudes above 3,000 feet (900 meters), have a dealer
perform this carburetor modication. This engine, when operated at high altitude with the carburetor
modications for high altitude use, will meet each emission standard throughout its useful life. Even with
carburetor modication, engine horsepower will decrease by about 3.5% for each 1,000-foot (300-meter)
increase in altitude. The eect of altitude on horsepower will be greater than this if no carburetor
modication is made.
When the carburetor has been modied for high altitude operation, the air/fuel mixture will be too lean for
low altitude use. Operation at altitudes below 3,000 feet (900 meters) with a modied carburetor may cause
the engine to overheat and result in serious engine damage.
Note: Jet kits available for purchase upon request, please contact us at 844-DUROMAX to set up your
parts order.
ENGINE SETUP (CONTINUED)