Predator 173 cc service and mower replacement fit
For Predator 173 cc item 69731, the manual specifies 0.6 USquart oil and DCPR7E, DK7RTC or RA8HC plugs gapped 0.027–0.031 inch. It is a vertical mower engine. Check shaft diameter, length, mounting and brake controls before replacing another engine; a matching displacement does not establish a safe fit.
Measure the shaft and keep the engine brake
The item 69731 manual lists a 7/8-inch shaft, 3.16-inch length, 3/16-inch keyway and 3/8-24 tapped end. Its installation chapter requires the mower’s brake cable and emergency-stop arrangement to function. Do not weaken its brake spring to make a mismatched handle easier to pull.
Consider a hypothetical deck with a 3/4-inch blade-adapter bore. The 69731’s 7/8-inch shaft is 1/8 inch larger in diameter, so the adapter does not fit as supplied. That dimension check rejects the pairing before a buyer spends money on a carburetor, blade or mounting hardware.
Keep the oil and plug record item-specific
The manual lists 10W-30 above 32°F and 5W-30 at or below it. Its operational break-in is about three hours without heavy loading; its first oil change follows approximately 20 hours. Later oil service uses the six-month/100-hour schedule, with closer air-cleaner attention in dust.
Check oil before use, with the engine stopped and upright. For plug work, disconnect the cap and let the engine cool. Valve clearance and fuel-system service require the qualifications and procedure in the matching manual, rather than a general mower-engine setting.
Order against the UPC as well as the item
Harbor Freight’s parts lookup identifies 69731 with UPC792363697316. A seller grouping 69731 and 71413 together does not establish that every individual assembly is interchangeable. Photograph the label and compare the actual parts diagram before ordering.
For repair-versus-replacement budgeting, include the blade adapter, controls and qualified installation if any are incompatible. An inexpensive bare engine can cost more than a repair after those required components are included.
Predator 173cc vertical engine: oil, spark plug, valve clearance and maintenance schedule
The Harbor Freight PREDATOR 173cc vertical engine takes 0.6 quart of oil, SAE 10W-30 above 32 degrees Fahrenheit and 5W-30 at or below it, changed after about 20 hours of use. The spark plug is an NGK DCPR7E, Torch DK7RTC or Champion RA8HC gapped 0.027 to 0.031 inch, valve clearance is 0.004 to 0.006 inch on the intake and 0.006 to 0.008 on the exhaust, and idle is 1,800 RPM.
Remove the spark plug cap before any inspection, cleaning or maintenance, and wait for the engine to cool before changing the oil.
The 173 cc vertical engine on one table
The PREDATOR 173cc is a vertical-shaft engine built to replace the engine on a walk-behind mower, with a 7/8 inch by 3.16 inch shaft, an 8 inch mounting base pattern and forced air cooling. It is a small engine, with a 0.25 gallon tank that runs about 40 minutes at 50 percent load. The manual notes that in California it is for use only on construction or farm equipment.
| Item | Specification |
|---|---|
| Engine oil | SAE 10W-30 above 32°F; SAE 5W-30 at 32°F or below |
| Oil capacity | 0.6 quart |
| Fuel | 87 octane or higher, stabilizer-treated unleaded gasoline; no more than 10% ethanol, no E85; tank 0.25 gallon (0.95 L) |
| Spark plug | NGK DCPR7E, Torch DK7RTC or Champion RA8HC |
| Spark plug gap | 0.027 to 0.031 in |
| Valve clearance | Intake 0.004 to 0.006 in; exhaust 0.006 to 0.008 in |
| Idle speed | 1,800 ± 50 RPM |
| Bore, stroke and compression | 70 mm x 45 mm; 7.9:1 |
| Sound level | 104 dB |
Break-in and the first oil change
The manual gives two break-in periods. The operational break-in lasts about three hours, when you should not apply a heavy load. The maintenance break-in lasts about 20 hours, and after it you change the engine oil.
After that the schedule follows. The manual warns that the engine must be started every three months and allowed to run in storage, and that you should not use gasoline stored in a metal fuel container or a dirty one.
The Predator 173cc vertical engine schedule
| When | What |
|---|---|
| Before each use | Brush off the outside of the engine and check the oil level, the air cleaner and the deposit cup. |
| Monthly or every 20 hours | Change the engine oil (the first change). |
| Every 3 months or 50 hours | Clean or replace the air cleaner; service it more often in dust. |
| Every 6 months or 100 hours | Change the oil, check the deposit cup, clean or replace the air cleaner, and check and clean the spark plug. |
| Yearly or every 300 hours | Have a qualified technician check idle speed and valve clearance, clean the fuel tank, strainer and carburetor, and clean carbon from the combustion chamber. |
| Every 2 years | Replace the fuel line if necessary (technician). |
Parts to buy for the Predator 173cc vertical engine
| Part | Part number | Notes |
|---|---|---|
| Spark plug | NGK DCPR7E | Or Torch DK7RTC or Champion RA8HC. Gap 0.027 to 0.031 in. |
| Air filter and plug kit | Amazon B0GYP4HMNZ | For the 69731 and 71413 173cc engines. |
| Engine oil | SAE 10W-30 | 0.6 qt above 32°F; 5W-30 at or below. No oil filter on this engine. |
0.6 qt
Oil capacity
10W-30 above 32°F, 5W-30 at or below.
DCPR7E
NGK plug
Or Torch DK7RTC or Champion RA8HC. Gap 0.027 to 0.031 in.
20 hours
First oil change
After the break-in, then follow the schedule.
What the Predator 173cc is specified as, and what it replaces
Harbor Freight's listing gives the engine as 5.5 HP at up to 3,200 RPM with 6.6 ft-lb of torque at 2,500 RPM, vertical mounting and 87+ octane unleaded fuel, and names it as a replacement for the Honda GXV160 and GCV170 and several Briggs & Stratton 150 to 175 cc engines.
Because it is sold as a mower replacement, check the shaft length and mounting pattern against the engine being replaced before you order, and use the oil and plug specifications on this page for service.
Fitting a Predator 173 to a mower: the manual's installation rules
Unlike most engine pages, this one has an installation chapter in the item 69731 manual. It says to install the engine on a lawn mower only, never to power a vehicle, and to have a qualified technician do it if you have any doubt.
The mounting pattern is one 3/8 inch by 24 threaded hole, 1 inch deep, and two unthreaded holes of 0.34 inch (8.7 mm) that take 5/16 inch (8 mm) hardware. Set the engine upright, line up at least three mounting holes with the mower deck, and use hardened stainless steel bolts, lock washers and washers of a suitable length, making sure the hardware cannot touch moving parts.
Some decks may need a hole drilled or a mounting plate made, which the manual says only a qualified technician should attempt.
For controls, the mower's brake cable sheath goes through the hole in the brake bracket, the cable attaches to the brake arm, and the sheath is adjusted with the nuts to take up all slack. The manual stresses that the engine brake is an emergency shutoff and that you must not replace the brake spring with a weaker one. If the brake handle is too hard to operate, a technician has to fit a different handle on the mower.
The throttle cable attaches to the throttle control using the bracket and bolt, and the belt pulley or drive gear on the output shaft is fitted according to the mower's own service manual.
Predator 173 high altitude kit: what changing the main jet involves
The manual says the warranty is void if the necessary adjustments are not made for high altitude use. Above 3,000 feet it calls for an altitude kit installed by a qualified mechanic, and it says that above 8,000 feet the engine may lose performance even with the proper main jet. Running without the kit at altitude may increase emissions and reduce fuel economy and performance.
The kit contains a main jet for 3,000 to 6,000 feet, a main jet for 6,000 to 8,000 feet, a bolt seal and two fuel cup seals.
The steps are to turn off the engine, close the fuel valve, place a bowl under the fuel cup, unthread the bolt holding the fuel cup and remove the bolt, bolt seal, fuel cup, fuel cup seal and main jet, using a carburetor screwdriver that is not included. The mixing tube is held in place by the main jet and may fall out, in which case it goes back in the same orientation. Replace the jet for your altitude range and fit new seals, since the old ones may be damaged.
Finger tighten the bolt first so it does not cross thread, wipe up spilled fuel, and do not start the engine while you can still smell fuel. The manual also marks the engine as California only for construction or farm equipment.
Predator 173 against the Predator 212
Harbor Freight's manuals show that the vertical 173 cc and the horizontal 212 cc engines are not interchangeable. The 173 has a 7/8 inch by 3.16 inch shaft with a 3/16 inch keyway and a 3/8-24 tapped end and mounts on an 8 inch (203 mm) pattern, and it turns counterclockwise viewed from the shaft. The 212 has a 3/4 inch by 2.41 inch shaft, also with a 3/16 inch keyway but a 5/16-24 tapped end.
Its 0.25 gallon (0.95 liter) tank and 40 minute run time at 50% load also show that it is a mower engine, not a general purpose one, and its 104 dB sound level is a reminder to wear hearing protection. Both engines idle at 1,800 RPM and both take 10W-30 above 32°F and 5W-30 at or below, so the oil carries across between them, but the pulley, blade adapter and mounting do not.
Predator 173cc vertical engine: questions
How much oil does a Predator 173cc engine take?
The owner’s manual gives 0.6 quart. Use SAE 10W-30 above 32 degrees Fahrenheit and SAE 5W-30 at or below. Reinsert the dipstick without threading it in to read the level, fill to the full mark, and thread it back in clockwise.
Do not overfill.
When should I change the oil on a new Predator 173cc?
After the maintenance break-in period, which the manual says lasts about 20 hours of use. The operational break-in lasts about three hours, during which you should not apply a heavy load to the equipment. After the first change, follow the maintenance schedule in the manual.
What spark plug does a Predator 173cc use?
The manual lists an NGK DCPR7E, a Torch DK7RTC or a Champion RA8HC, with a gap of 0.027 to 0.031 inch. It warns that an incorrect plug may damage the engine, and to adjust the gap without prying against the electrode.
What are the valve clearances on a Predator 173cc?
0.004 to 0.006 inch on the intake and 0.006 to 0.008 inch on the exhaust. The manual marks checking and adjusting valve clearance as a job for a qualified technician. Idle speed is 1,800 RPM, plus or minus 50, and the compression ratio is 7.9 to 1.
How big is the fuel tank on a Predator 173cc?
0.25 gallon, or 0.95 liter. The manual gives a run time of about 40 minutes at 50 percent load on a full tank. It specifies 87 octane or higher unleaded gasoline treated with a fuel stabilizer, with no more than 10 percent ethanol and no E85.
Can I put a Predator 173cc on my lawn mower?
It is a vertical-shaft engine with a 7/8 inch by 3.16 inch shaft, a 3/16 inch keyway and an 8 inch mounting pattern with a 3/8-24 tapped hole, so it fits mowers built for that pattern. The manual has mounting steps for the throttle and brake cable. Check the shaft and bolt pattern first.
Is the Predator 173cc legal in California?
The manual says it is for use only on construction or farm equipment in California. It states the emission control system is warranted to standards set by the U.S. EPA, and that the engine is EPA phase III compliant.
Read the emissions warranty at the end of the manual.
How do I clean the air filter on a Predator 173cc?
The maintenance list says to clean or replace the air cleaner, and to service it more often when used in dusty areas. Remove the cover and elements, check them for dirt, and clean and dry them. Running without a filter lets dirt into the engine and causes rapid wear.
Why does my Predator 173cc need starting every three months?
The manual’s storage section says the engine must be started every three months and allowed to run, so fuel moves through the carburetor and the parts stay lubricated. It also says to put a tablespoon of engine oil into the cylinder through the plug hole for longer storage.
What engine noise figure is specified for the Predator 173cc?
The specification chart lists a sound level of 104 decibels. That is loud enough to need hearing protection during a long run. The engine turns counterclockwise as viewed from the power takeoff, and the manual’s break-in advice is not to run it at high load for the first three hours.
What is the Predator 173cc bore and stroke?
70 millimeters by 45 millimeters, giving a displacement of 173 cc and a compression ratio of 7.9 to 1. It is a forced air-cooled four-stroke. Those figures are printed in the same chart as the oil and plug specifications.
What is the difference between the Predator 173cc and 212cc?
The 173cc is a vertical-shaft engine with a 0.6 quart sump and a DCPR7E plug, and the 212cc is a horizontal-shaft engine with a half-quart sump and a BP-6ES plug. Their valve clearances and schedules also differ, so use the manual for the one you own.