Predator 3500 Watt Inverter Generator

[RonT]

I made an unexpected purchase of a Harbor Freight Predator 3500 inverter generator during my recent travels through the midwest when my Onan 4KW microquiet generator failed during the July 2019 heatwave in Indiana. Now that I have it, I thought I'd share my experiences (good and bad) for what it's worth.

Break-in - I used HD Rotella 10w30 for the higher concentration of anti-wear additives. Oil was changed at 8, 30 and 50 hours. There were no visible 'sparklies" in the oil drained for the 50 hour change. I swapped to Rotella synthetic 10w30 at that time.

Positives:
Price - With a coupon, this generator was $700 compared to nearly $2,000 for the Honda equivalent.
Capacity - Rated for 3,000 watts continuous. This generator easily powered my RV air conditioning and appliances.
Connectivity - This generator has a 120V 30A outlet and came ready to plug in our RV with the adapter included.
Quiet - This generator is really quiet - way quieter than the installed Onan. If load is light - the eco throttle setting is even quieter.
Features - Digital info panel with voltage, current, wattage, total engine hours, session engine hours/minutes, overload, maintenance required and over/under voltage.
Electric and pull start - battery is supplied.
Oil drain has a removable floor plug and is designed to route the oil to this opening.
Engine - Honda clone 212cc engine that HF sells for cheap if it ever fails.

Negatives:
Operators manual - missing a couple of important pieces of information. The most notable being that if you fill the fuel tank to the top, the internal vent will fill the charcoal canister with gasoline and cause the engine to run very rich and eventually shut down (more about that later).
Cooling / combustion air inlet - Located just under the front of the generator about 1-2 inches off the ground. If you run this sitting in the grass, you are restricting air flow. If you run this in an area with debris - it will suck it up and put it who knows where. I set this end on plywood to keep the air flowing. There are "big wheel" kits that might take care of this problem.
California emission controls - This generator has a charcoal canister which purges to the carb inlet with no metering. If the canister gets loaded with fuel, it's like running with the choke on. (more on this later).
Oil fill - PIA as it is recessed quite a bit. A long funnel is supplied but you have to add the 18 ounces of oil slowly.
Small fuel capacity (2.6 gallons) - Not too bad if you are not running your AC all night long in a heat wave. I could only get about 5 hours in this case. The emission control design will not let you use an "extended run" external tank without some minor modifications.
Spark arrestor design - prone to sooting up and restricting / plugging exhaust if the engine runs rich.

With all of this being said, this generator saved my vacation and allowed me the flexibility to repair the Onan in my home shop (It was a stuck brush that was arcing badly - all fixed now).

Now for the embarrassing confession of my self inflicted problems (and solution) after the first over-night use.
Before retiring for the night, I refilled the generator filling the gas nearly to the top and went to bed. The manual said to leave room for expansion and since it was to run loaded all night, what could this hurt?
After a short time, I noticed that the generator was not running as smoothly. By morning I found that the generator would no longer power the air conditioning and would show the overload warning with very little load on the generator.
My first inclination was to take it back and exchange it - luckily the store was not open yet which gave me some time to research the issue. Following the troubleshooting guide in the manual, I found that the spark plug was black and fouled and the spark arrestor was completely plugged with sooty carbon. I also found that the air filter was very damp with raw gasoline. A little research on the web revealed the cause - the gas tank is vented through a charcoal filter (just like your car) to the inlet of the carburetor. When I over filled the gas tank, I saturated the charcoal canister with gasoline, making the engine run very rich and lose power as the spark arrestor plugged up the exhaust.
The manual really ought to have a large bold warning that overfilling will overload the pollution control system and cause the generator to fail!!!

Disclaimer - this is how I fixed my generator when I screwed it up - your results my vary. The fix was relatively simple but took a couple of hours.
1 - ensure the gas tank is not overfilled.
2 - purge the gas and vapors out of the charcoal canister with dry compressed air.
3 - Clean or replace the spark plug (NGK BPR7ES).
4 - Remove and thoroughly clean both spark arrestor screens.
5 - With the spark arrestor removed (to allow the soot and carbon to be purged), run at least one tank of fuel through the generator at a moderate load.
6 - Replace the spark arrestor. (its a bit noisier without it but some areas we camp at require it to be installed)
So far after doing this, my generator was used for the rest of our trip and has been running without any issues. The RV generator is now fixed but this one is so darn quiet I will probably be using it for overnight when needed.

After I get some more run time on this generator I will likely perform some simple modifications to allow hooking up to an extended run tank.

Bottom line - Although I had no intention of purchasing this generator, I'm very pleased with it and can recommend it provided you heed the information provided above.

Ron

[ricky racer]

Great review!! Thanks for posting!

[outdoors4evr]

Excellent! I love "the good" "the bad" and "the ugly" review!

[Rick Spivey]

Thanks, Ron. I also have had a Chinese knock-off engine powered generator (also a predator, I believe, but purchased at Norther Tool). I don't use it a lot, but have been very pleased with that engine (Honda clone) thus far. It may crap out tomorrow, but so far so good, and it got me through an ice storm with no issues.

[Urbish]

Excellent review. Thanks for the tips and insight. Now you have me regretting spending the 'big bucks' on a NorthStar (Honda powered) 6500W from Northern Tool. As luck would have it, I bought it two years ago after an extended power outage and the power hasn't gone out since. But it fires up on the first pull every month when I run it and perform PMCS. So I am confident it will be at the ready when I need it!

[outdoors4evr]

I bought it two years ago after an extended power outage and the power hasn't gone out since

Best insurance policy you have every purchased!
I did the same after a week long outage in 2003. https://www.theatlantic.com/photo/2018/08/photos-15-years-since-the-2003-northeast-blackout/567410/