Question of of the day 10-14-13

Utterpower's grid generator

Utterpower’s offgrid pump house


Hello, I bought an AURORA 6500 diesel generator in 2009. When I had the manual transfer switch installed in the house, the electrician told me to have my generator looked at. Well, I have had one disappointing experience after another !

I have read some of your articles and I feel my situation might finally have a tolerable end.
In order to achieve the 60hz, this generator just about shakes apart. The engine also sounds bad as it sounds as if missing at 3600 rpm. It wants to run seemingly well below 3400 rpm’s. I would appreciate any advice. Thank you

Answer: First, I attempt to answer your question and then I’ll ramble on some.. (as I normally do ūüôā

I think some of these designs are pushed past their design limits to meet our 60hz standard with a two pole head. Gravity fuel¬†systems might need to be set higher to deliver all the fuel required, and in stationary applications, the first thing we do is strip anything we can off the generator frame! The fuel tank can be¬†full of¬†bubbles, and as I mention way too low to keep your beast properly fed as such a high RPM. Gauges and other things… take them off the frame and mount them on the wall, keep them from rattling apart as many do.

Once you improve your fuel system, and you might add a lift pump.¬†If the¬†problem of not being able to maintain 60hz or near persists, then it’s time to look at your governor..

George’s Muse Follows..

First you need keep in mind, you solicit the opinion of a student, never to be the cocksure master we find in such numbers, and of course most of them have wares to sell.

When we deploy Diesels, we do so knowing the advantages, a fuel that stores for years when properly treated in a fuel system that doesn’t breathe. WE know of the fuel density, more BTUs per volume, and even our ability to manufacture a suitable alternative fuel if we desire.

Beyond that, we know that diesels CAN be built to produce torque at very low RPM, and many outlast their owners. At first direct drive between prime mover and generator head sounds like an advantage, but this doesn’t allow us to optimize our power plant for the loads >WE< typically run, which can greatly improve BTU/KWH conversions. Even a reduction of 200 RPMs can make all the difference in longevity, and it can improve fuel/KWH conversion figures in our typical operating range.

A gen set too large, is normally a bigger mistake than one too small, and the well pump generally the load that MUST be started.

A larger engine running a bit slower, and coupled via an efficient transmission allows us to use off the shelf common parts, and avoid expensive 8 pole heads and the like. And we run the engine well below that nerve racking speed that produces top HP rating.

It helps to visualize the game of more fully loading each power pulse, and still operating within the operating range of the governor, and sometimes we need make a spring change to a lighter one, if we are to get the best response to load coming and going.

Hands on experience¬†is how we learn, and it is powerful¬†as per changing our opinions. But what to do if you don’t like what you have? It really depends on how handy you are. Some find it best to sell what they have and start over. When you come across two bearing generators of decent quality, you have a major part of something you can build and tune to you liking… that’s if you’re a one percenter.. the other 99 percent shop the big box store..

Always the student..


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7 Responses to Question of of the day 10-14-13

  1. Daniel Moore says:

    Thank you for the reply. I will experiment with this some more.
    Since 2009 ; I have become even more convinced of my choice in Diesel power. I bought a smaller kW but more robust generator, a military 3kw. It seems to suit me well we just manage within our limits. I use up the feul throughout the year as my lawn mower is diesel . I was just trying to get a back up use from the Aurora. I wouldn’t sell it as I believe it does not work as it should. Also, I have had No luck having the thing repaired/fixed.

  2. George B. says:

    3KW has been my target power production for years, as for the other gen set, there are always folks optimistic they can fix it and be happy with it.. I’d still consider selling it (as is) and telling perspective buyers you think it needs attention..

  3. David says:

    I had to google that generator to see what it was. As I suspected, just another Chinese rebranded unit.

    I have a number of these Chinese Vertical ( and Horizontal ) and none of them have been right from the word go.

    All the various ones I have came with incorrect setting of the injector pump. As far as I’m aware, the only thing you can adjust on them in the spacing from the block. This must affect timing I think as they run direct on the cam and spacing them out makes a BIG difference.

    One of my engines was just plain wrong.
    There is diesel clatter and there are the sounds of self destruction which was what was coming from this engine. It had some copper spacers under the IP so I put them on my scanner and printed the outline on cardboard and cut them out. ( A handy way I found to make small gaskets when you can copy an original or a scan a small part. )

    I made a good number of the things and cut and punched them out and added them under the pump . Eventually the thing settled down and ran sweetly. It then occurred to me that maybe I upset something by running veg oil in the thing so I put it back to diesel which was fine. I then removed the spacers and the thing made so much clatter I wondered if I had done something wrong. You could hear it ringing like a bell.
    Put the gaskets back under the pump and it turned into a kitten again.

    Loading up an induction motor with this engine driving it shows more power than I think I should get before it smokes so it does not appear to be too retarded.

    The other thing with these engines is Valve clearance. I was playing with another engine of the same type just yesterday and noticed it was smoking unexplainedly and
    and seemed to be lacking the edge on it’s output.
    Turning it over I could hear the compression escaping. Removing the muffler confirmed that. Took off the rocker cover and noticed the exhaust vale was tight. I backed it off to a small gap, sighted only and turned the thing again and the compression escape was barely audible from inside the engine.

    Fired it up and the smoking stopped. Didn’t load it up to test power but obviously it won’t have gone backwards.

    I agrree with Georges comment about the fuel tanks too. I have commented previously on the leaky china designs but what I have also found as different to a height issue is a fuel flow issue through the tap and filter. Many engines have an internal filter which seems to flow marginally at best and restrictive with anything more viscous than thin Diesel. I have pulled out and chucked all the internal filters where fitted and just put the inline disposable paper filters from the auto accesories place in the line before the pump.

    Some of the fuel taps I have also 86’ed ( along with leaky tanks!) and one I managed to drill out internally for a bit more flow. Helps when you are running veg oils.

    To the best of my knowledge, those china verticals only came up to 10 HP so hooking one up to a 6500w Genny seems a stretch from the outset unless that is a Typical Chinese big number rating which is the output for 2 Sec if you rev the thing flat out and then dump the load on it and take advantage of inertia.
    5Kw would be a much more comfortable load for these engines.

    Unless they are over loaded, I would expect they should run quite smooth and rev willingly. Mine do and while I don’t have a tach to measure, I would not be surprised if the things exceed 5000 Rpm unloaded. Pulling 3600 shouldn’t be a problem except for the racket.

    One last thing, Check the exhaust. I was looking at one of mine yesterday and the exhaust comes out of the head has about an inch of space in the manifold and then takes a 90o turn. Can’t be good for efficiency. I’m going to look for a flange at an exhaust place or make one so I can modify the thing so the gas has a much smoother and subtle path to follow. I don’t know it will mean any more power but I don’t think it will hurt or with getting heat out of and away from the engine faster.

    Over all I think these cheap and cheerful engines are quite good but like a lot of these things from Places like china and india, they lack finish and “tuning” to make the best of the core unit.

    A bit of massaging makes a lot of Difference in my experience.

    As an aside, some time back I was given an Old Genny powered by a briggs motor. Not to upset the patriotic readers I won’t go near what I think of Briggs engines but wondering how many things would be against an engine transplant on the gen head, I realised this motor has a gear reduction on it. That would make it a 4 pole head that would run at 1500 for our power.

    I can’t read the nameplate on the genny but It has an 11 HP motor so I’m wondering if they still went by rule of thumb and halved the kw of the hear or took advantage of the gearing and bumped it up a bit?

    • David Pearce says:

      I think the Aurora generators are “buyer beware”. They scrub their site, youtube, and various websites for negative reviews, I assume, since almost any manufactured products is going to tick someone off at some point, and yet, this is the first negative review I have read about the Aurora stuff. But given the image they attempt to maintain on the net, I guessed it.

      I don’t trust companies like that. If there are negative reviews, they need to review the reviews and work with their provider in China to improve aspects that are coming up.

      • George B. says:

        We all see the world differently, I see the CF186 as a prime mover to make a 4kw continuous rated generator, and I’d never recommend more than 3000 rpms. But as I mention over and over, my tribe is the DIYer, we are one percent of the population.. few will ever design for us, we need do it ourselves. An external governor spring change may be all you need IF you run the engine slow and find the governor a little sluggish.

  4. Brett Price says:

    Hi George, Recently purchased an ST12 here on east coast set for 240VAC, the rheostat replaced by an AVR. We are seeing it requires upward 5 horse power 1800 RPM just to create the excite field 80 VDC 6.1 amps. That requires over 3730 Watts just to excite the field before any outside load has been applied. The field measures 17.8 ohms and the stator 4.1 ohms, the rectifier checks good on diode check. We also checked there are no high resistance or shorted windings to ground. The excite field is (80VDC@6.1amps) = 488 watts albeit that does not count for expected reluctance of rotor magnetic lines of force pushing electrons in the stator or the moving the weight of the rotor however 488 watts is a far cry from 3730 watts. With the field disconnected from rectifier ST12 required roughly 560 watts to maintain 1830 RPM. The question being is 5 horse power (3730 watts) a typical load while AC is unloaded or might there be some underlying issue at hand? Thanks for assistance!

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