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Two Stroke 1kW Generator Test


A few days ago on rec.outdoors.rv-travel (RORT) someone asked about the capacity of my little 2-stroke generator. He also asked how much juice my little electric chainsaw consumes and how well it operates with the generator.

So, dear readers, I decided today to brave the cold winter weather of the mountains here in Tellico Plains (actually I love the weather but this sounds better) to instrument this little combination.

My instrument of choice for this test is the Watts Up Pro ES. This instrument isn’t my normal first choice, that being a Kill-A-Watt but in this case, the cord on the WUP and the display buried inside the case where it works better in the cold won the day. This instrument behaves badly on low power factor loads but the chain saw in question is of fairly high power factor so the meter is fine.

Test SetupHere is the test setup. (click photos to enlarge) On the left is the WUP. In the center is the little $39.00 electric chain saw that I bought several years ago thinking that it would be a one-season-wonder. Several years later it is still running fine. On the right is the UST 1kW generator. It is the same generator sold widely around the net for about $100. For example, Northern Tool. You’ll notice that mine is red while the NT one is blue. That’s cuz the Chicoms will paint it any color you want. I have a NT unit and it is identical in all but cosmetic respects to this one.

Test Plan

The plan was to take three readings,

I used the WUP’s capability to capture peak watts to acquire the data while I was busy operating the saw. I should add that the temperature was 30 degrees and the sea level corrected baro pressure was 30.58, altitude 1950 feet. The cold air should make the generator look good, while the altitude detracts a little and the cold makes the saw draw a little more power. Since I’m not writing a paper to be published in Nature, we won’t try to compute any normalizations.

Idle power

Saw idlingHere is the saw idling. Since the saw contains a universal motor and since a universal motor, like all series motors, speed up with lessened loads, it’s not surprising to find the saw running very fast and drawing almost 3/4HP. The generator sounded like it was a bit loaded but not enough to increase the noise any.

Normal Sawing

Routine cuttingHere I was sawing normally, cutting through an about 5″ diameter log. I wasn’t being particularly careful about loading, simply sawing like I normally do. The saw is drawing almost exactly 1 hp (that being 746 watts) and the generator sounds fairly heavily loaded.

Highest Load

Maximum LoadFor this test I located the WUP where I could see it and worked the saw aggressively into the wood until I achieved the maximum wattage I could. The generator was fully loaded and sounded like it had slowed some. Unfortunately this instrument doesn’t easily capture frequency so I don’t know how low. Subjectively, not all that much.

This is about 1.4 electrical horsepower. This tells us several things:

  1. The generator meets its nominal rating of 1kW.
  2. The claims seen in some e-stores that this is a 1200 watt generator are false. The generator was obviously at the higher load that it could support and maintain some semblance of 60 hz output.
  3. It lays to rest some claims that have been made that this generator cannot output a kW.

My homemade electric lawnmower that I also operate from the generator draws a bit more power, judging by how it loads the generator down in heavy grass. The generator has obviously slowed down considerably and the output power is far out of spec. Nonetheless, it operates my mower just fine. Take that, Honda! :-)

I was going to test my mower but for two problems. One, no grass this time of year and two, it’s packed away deeply in my basement and will require a SAR operation come spring. I’ll get back then.

Oh, and before you ask, the reason I use an electric lawn mower with a generator instead of just using a gas lawnmower is simple. The whole electric mower weighs perhaps 20 and no more than 30 lbs. Second, when I’m close enough to the house, which is most of the time,I use shore power. Generator power is strictly for when I’m too far away.

I had planned on operating and instrumenting a 1,000 watt metal-halide light on the generator and document the results but alas, the little generator ran out of gas, my feet were getting cold and more gas was on the other side of my property. We’ll save that one for a later day too.

—— 01/23/2008——

I received a question concerning the model number and nameplate of the Northern Tool generator, the blue one. This is not the generator that I tested but it is in every way identical to the red one except for cosmetics. In response, here is a photograph of the nameplate.

Northern Tool Blue generator nameplate

Yep, Northern highly over-specs this generator. A shame, as it is a competent 1kW generator.


Posted by neonjohn on January 21st, 2008 under Power Generation, RV/Camping

9 Responses to “Two Stroke 1kW Generator Test”

  1. Neon’s Glow - The Blog of John DeArmond » BlogDesk Mysterious error and solution Says:

    […] I started working on my 1kW generator test post. When I finished it and tried to transmit it to my blog, I got this meaningless […]

  2. Matt Colie Says:


    The test is real clear. It is obvious that the device meets specification. If it had not done what they said it would, then it would be nice to have actual baro (I can figure that out with altitude), Dry bulb (you got), Wet bulb (to know real humidity) and the fuel quality. So, for not being a lab guy, you hit pretty close. Since it made spec at your test conditions, Who cares? Too bad you didn’t have someplace just to plug in the Kill-a-Watt. I would have liked to know how far the frequency sagged.

  3. David Gearhart Says:

    Interesting test of a possibly useful new product. But I worry about the chainsaw engine. A Chinese chainsaw engine?? How long will it last.
    A friend of mine who owns a Husqvarna chainsaw shop told me once that the average life of a chainsaw is unbelievably short in the hands of the average person. ( If there is such a thing!) I believe it was under 10 hr of actual cutting!!!!

  4. neonjohn Says:


    This little generator has been around for a long time. I got the red one in 2001. Internally, it looks similar to a 2 stroke motorcycle engine – all ball and needle bearings. I have put probably 200 hours on the little thing already.

    Low end 2-strokes are a whole ‘nuther matter. When I started working on the Cordless Battery Charger I looked at 2-stroke engines. My target weight of the first unit was 10 lbs or less.
    I learned quickly that these engines have lifetime ratings. The low end half-crank weed whacker engines that only have one main bearing and only a half of a crankshaft are designed typically to last 40 hours.
    These are the engines that end up in the loss-leader weed whackers and chain saws.


  5. Bruce Says:

    Re: Two stroke generator. Is the one above the same as the one here:

    that’s selling at Kragens for $99? I bought one and it works great, but it’s a little hard to start (no problem though if I use the aerosol starter spray).


  6. Bruce Says:

    By the way, I’m not behind that ad at the link in the previous message. Just found it thru Google. The link at Kragen’s (Partsamerica) you have to log in before you can get to it so I can’t post a straight link.


  7. neonjohn Says:


    Yep, same generator. STILL not capable of 1200 watts.

    I’m going to get some spare time soon and I’m going to take a look at the hard starting problem. I THINK it’s a lack of sufficient choke. It starts pretty easily when I hold the choke lever fully over and starts even better if I stick my thumb in the carb opening for the first pull. There’s a little hole in the choke plate. It may be that all I have to do is plug that.


  8. Nick Says:

    I have a UST 950 W generator purchased at Pep Boys….much the same as above. I have serious starting problems…but once started and with the choke left partially on, it runs well. My question is about the 30:1 gas:oil ratio. Can this be right? I have seen the identical generator on other web sites (different color tanks) claiming 40:1 or even 50:1. There seems to be nowhere to go on the web to get information on these UST units. Any ideas?

  9. Greg Says:

    I run mine on the 40/1 I put in my dirt bike. 5 years now never a hitch. I start it full choke third pull, boom. make sure and turn the pitcock to off when your done and let it run out of gas. Otherwise the gas evaporates in the bowl leaving residue that clogs the jets and fuel pickup.

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