Harbor Freight Predator 4375 Generator 63960 63961 not same which one is better?

avi

Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Hi all, I am a software guy, and these are my first ever small engines... (i.e. I don't even know what I don't know about small engines) For redundant redundancy I decided to get two HF Predator generators, so I'll have a hot spare, or if I might need more power. By chance I ended up getting item# 63960 and item# 63961 (the CARB versions of the 4375) they look cosmetically different, and they are obviously from a different supplier from minor stuff such as the 61 gas tank filler is offset to one side, while the 60 has it centered the tubular frame has the cross members at a different locations on top the cover of the pull cord on the 61 is red, while the 60 is black. to some stuff which might indicate better quality: the 61 valve cover is cast while the 60 is stamped metal the 61 air filter box is stamped metal, while the 60 is plastic the casting of the engine body seems better on the 61, sharper corners, vs more rounded off/sloppy casting. (also the etching of the serial number etc seems better/sharper on the 61) the carburetor also seems better manufactured on the 61 they both started on the first pull (actually not even a full pull) the 61 kept running at closed choke, though sounded bit "sickly", so I switched the choke to "run mode" fairly quickly the 60 was very rough at closed choke and I had to switch it to "run mode" right away however, the biggest difference is the RPM, as measured by an inductive tachometer/Hour meter which has an inductive wire looped around the spark plug wire the 63961 is showing 1800 RPM while the 63960 is showing 3600 RPM... yet they both sounded to me as they were running at the same pitch. I happen to have a third spare tach, and hooked it temporarily to each engine in turn. the results were about the same 1800/3600 readings (not as stable reading, probably because not as many inductive loops on the temporary tach) I do not have a scope to measure the sinewave output, but I do have a "true sine wave" UPS. when hooked to the 63961 and under load the UPS was running off the generator, with an indicated 121V input, and output at 121v and 60-61hz (a bit jittery) however, when hooked to the 63960 and under load, the UPS switched to battery power, with an indicated 117v input but since on battery power, showed an output of 120v at 60hz could it be that the two engines are really running at different RPMs even though to an untrained ear they sounded about the same??? or could it be that the 63961 fires up the spark plug on the power downstroke, while the 63960 fires up on both downstrokes??? to me, the 63961 seems "better": better made, and possibly running at a lower RPM, should I attempt to exchange the 63960 for a second 63961? or for the sake of redundant redundancy, keep the two different ones? thanks and a happy new year. -avi
 
Joined
Jun 15, 2003
Messages
36,804
Location
ME
There should be a governor screw you can mess with to get the 60 up in speed by a hair. (Or another hole for a spring.) Or maybe it can be adjusted under warranty-- HF would probably send it off to "purgatory" and give you a replacement then later sell it as open-box. I would run my house and computers off 117V/ 59Hz if that's what I had.
 
Joined
Mar 18, 2008
Messages
6,638
Location
South Florida
One of them fires the spark plug on the exhaust stroke, so two sparks per 4 of the strokes. This is pretty common. They both are running at 3600 rpm, guaranteed.
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by bubbatime
One of them fires the spark plug on the exhaust stroke, so two sparks per 4 of the strokes. This is pretty common. They both are running at 3600 rpm, guaranteed.
Thanks, that is why both sounded at about the same pitch. Questions Any advantage/disadvantage to firing on the exhaust stroke? is it true that most engines only fire once per 4 strokes? If so I'd assume that the tach would compensate and double up the count of the sparks? ie I should be seeing 3600 and 7200?
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by eljefino
There should be a governor screw you can mess with to get the 60 up in speed by a hair. I would run my house and computers off 117V/ 59Hz if that's what I had.
Thanks I am not concerned about the minor variations or the jitter I adjusted the governor screws so that the one showing about 1800 was mostly at 1800 under load and 1840 at no load. And the other one similarly mostly at 3600 under load The question was why the tach was showing double the RPM for one of the engines. And which one is better, if any?
 
Joined
Jun 15, 2003
Messages
36,804
Location
ME
The magneto was giving a waste spark, which, if I were engineering things, would be how I would expect it to work! The crank turns 3600 RPM so the magnets etc would be rolling by every revolution. The 1800 RPM (indicated) might have some sort of more-advanced electronic ignition. It would have to "know" power strokes vs non-power by looking at something besides just crank position. This would be reinventing the wheel. The "Tiny tach" is intended for small engines and its designers may be expecting the waste spark. Waste spark is a less powerful spark, because the spark doesn't have to jump through 9 atmospheres of pressure, as it's not at near TDC of a compression stroke. So that could send less (but not zero) energy through the wire, which may or may not be picked up, depending. What happens if you try switching spark plugs between the two engines? I wonder if you wound up with a non-resistor one in one. The resistor is only there for spark noise suppression, but it could be doing funky stuff with your tach pickup.
 

JRed

Site Donor 2021
Joined
Jun 1, 2009
Messages
2,592
Location
Virginia
Could the 63961 be a 4-pole generator? It would only need to turn at 1800 rpm if so, but there's usually an audible difference between 1800 rpm and 3600 rpm.
 
Joined
Dec 31, 2016
Messages
10,078
Location
Waco, TX
Originally Posted by JRed
Could the 63961 be a 4-pole generator? It would only need to turn at 1800 rpm if so, but there's usually an audible difference between 1800 rpm and 3600 rpm.
Harbor Freight does NOT sell any 1800 RPM generators (to my knowledge)
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by JRed
Could the 63961 be a 4-pole generator? It would only need to turn at 1800 rpm if so, but there's usually an audible difference between 1800 rpm and 3600 rpm.
I believe that electrically (the generator part) they are both the same One of the outlets is that large circular one with four slots and the extension cord that plugs into it has four regular sockets two for each pole.
 
Joined
Jul 7, 2008
Messages
1,473
Location
Maryland USA
Originally Posted by bubbatime
One of them fires the spark plug on the exhaust stroke, so two sparks per 4 of the strokes. This is pretty common. They both are running at 3600 rpm, guaranteed.
You should not have offered that bet !! I am not familiar with those generators, but in the marine world it is very common to have medium / large gensets running at 1800 rpm. 1800 x 2 = 3600 rpm. Some of them have gears that rotate the stater at 2x crankshaft, or use other means to convert the 1800 rpm to a perceived 3600. I cannot recall the name, but we used to have huge gensets that ran big v12 and v16 diesels , and they ran at 1800 rpm. I think the stators sometimes used odd configs that perhaps generated 2 hz per 1 crank rpm . I think some inverter gensets have a economy setting that runs the engine at low speed when demand is low, and the electronics convert the output to the proper frequency. In the absence of fancy electronics or gearing, the engine needs to run at 3600 rpm to provide the proper 60 hz frequency. The same basic generator can be made to supply 50 hz power for those regions where 50 is standard: the carb, governor and possibly the ECU is tweaked to provide the 3000 pm needed for for 50 hz power.
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by eljefino
The 1800 RPM (indicated) might have some sort of more-advanced electronic ignition. It would have to "know" power strokes vs non-power by looking at something besides just crank position. This would be reinventing the wheel.
Is one better than the other? I.e. electronic ignition vs standard magneto?
Originally Posted by eljefino
What happens if you try switching spark plugs between the two engines? I wonder if you wound up with a non-resistor one in one. The resistor is only there for spark noise suppression, but it could be doing funky stuff with your tach pickup.
I also purchased two NGK resistor spark plugs. I'll install them and report back (probably next Saturday)
 
Joined
Jul 7, 2008
Messages
1,473
Location
Maryland USA
From the Honda webset describing the advantages of inverter style generators- " Traditional generators have to run at 3600 RPM to produce 60 hertz (cycle) electricity. But generators with Eco-Throttle can run at much slower RPMs while maintaining frequency and power for the requested load. Because the engine does not have to run at full speed constantly, Eco- Throttle reduces fuel consumption by up to 40%. It also helps to reduce exhaust emissions. " https://powerequipment.honda.com/generators/inverter-generator-advantages
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by rubberchicken
Originally Posted by bubbatime
One of them fires the spark plug on the exhaust stroke, so two sparks per 4 of the strokes. This is pretty common. They both are running at 3600 rpm, guaranteed.
You should not have offered that bet !! I am not familiar with those generators, but in the marine world it is very common to have medium / large gensets running at 1800 rpm.
When researching whole house generators I've encountered 1800RPM generators but only on over 22KW which were much more expensive than 20KW and below, and I believe also water cooled. The Harbor Freight one I have are much smaller 4KW air cooled which have no fancy electronics aka inverter. Which is why they were only $320 each, about half the price of equivalent inverter generator I believe that only the inverter generators have the eco mode where the engine can run at variable RPM since the sine wave is created by the inverter and the generator might be generating DC power (not sure on that one)
 
Joined
Jul 7, 2008
Messages
1,473
Location
Maryland USA
I have seen a few inverter generators in the 1800 to 3000 watt range selling for $400-700 range, but they were off brands and probably Chinese knockoffs. Generac has a few inverter generators as well. The smallest 1800 rpm marine genset I saw was about 9kw. The big diesel 1800 rpm gensets were for standby power at large buildings and data centers, ranging from 750 kva to 1500 kva.
 
Joined
Jul 30, 2015
Messages
1,081
Location
Pennsylvania
These appear to be nearly identical generators for all intents and purposes. The only obvious difference in the specifications is that one is that one lists CARB compliance whereas the other lists CARB + EPA III. Just to echo what others have said, there is absolutely no way that one is running at 1800 RPM. That is simply not something you will find in gasoline powered generators at this price point. You can find it in diesel powered units if that spins your wheels. See http://www.centralmainediesel.com/diesel-generators.asp if you are interested. Now lets get to the problem you have yet to realize that you have. Inexpensive generators produce dirty power, and not all modern appliances will run on it. I've learned this the hard way. My Champion 4000 watt starting / 3500 watt running generator gave me numerous problems. The one likely to be relative to you is that the Cyberpower 1350 VA UPS backing up my network infrastructure machined gunned between line and backup, eventually causing my router and its attached 4TB drive to fail. Our gas range / convection oven have gotten flaky since running on the dirty power, and it seems that the logic board is going to need replacement. As for our front end loading washer and drier, all they would do on that dirty power was to make clicking sounds. We've recently added a Champion 3500 Inverter generator and now have no problems with the UPS. While we haven't tried the washer and drier, my suspicion is that both would work just fine with the inverter, At this point the Champion has been relegated to the backup to the backup, just as you are attempting to do. Now I know what to run and what not to run on the dirty power.
 

avi

Thread starter
Joined
Mar 2, 2009
Messages
16
Location
Camarillo, CA
Originally Posted by Astro_Guy
We've recently added a Champion 3500 Inverter generator and now have no problems with the UPS. While we haven't tried the washer and drier, my suspicion is that both would work just fine with the inverter, At this point the Champion has been relegated to the backup to the backup, just as you are attempting to do. Now I know what to run and what not to run on the dirty power.
Thanks, I already have these two non-inverter generators. is there a way to "clean up" the power? since the non-inverter generators were much cheaper than the inverter generator, I have about $300-$400 to spend on power cleaner for each generator and I'll still be ahead...
 
Last edited:
Joined
Sep 27, 2009
Messages
502
Location
indiana
The total harmonic distortion is probably high with those conventional generators. Likely around 20 - 25 percent. Ideally you do not want to exceed 5 percent. Inverter generators are less than 3 percent. It is possible to correct or clean up the THD but it's going to cost a lot more than your budget. Champion makes an open frame 3500 watt inverter generator with an eco mode for $500. I know it doesn't help you now but if in the future you decide to sell those and go with something else they're great generators. I have two and they work flawless. Being an electrician people ask me all the time what kind of generator they should buy and my answer for portable backup is an open frame inverter generator at minimum. They're very reasonable price wise now.
 
Top