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Generac Niagara 400 (watt) standby generator

Erstwhile

Apr 12, 2022
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Last summer I bought a (very) used 400 watt gasoline powered generator for $50.
The salesman (an auctioneer) said the former owner took "pretty good care of his stuff".
When I got it home and began to check it out, apparently the former owner had not changed
the motor oil when needed. (It was black and thick). After replacing the oil, the carburetor was partly disassembled and cleaned. The fuel tank was empty. The fuel lines were in a transitional state back to becoming whatever fossilized dinosaur they had been originally.
I ended up buying a replacement carb from Bezo's Barn, replacing the fuel line, air cleaner and filter, checking the spark plug and cleaning it. I found a schematic online.
https://www.jackssmallengines.com/j...electrical-schematic-wiring-diagram-no-61753#
The replacement carb did not work, but I couldn't return it because I used some pieces from it to try and repair the original carb. A month or so later I bought another (more expensive) replacement carb. Finally, the engine started and would remain running (if a bit fast). But the electrical outlets (120 VAC) only showed about 3 volts at high speed. So, with more web searching I found old generators need to be remagnetized to work properly. So, I followed that procedure, and there was no increase in voltage.
I started checking the charging circuit in more detail (Oops! There is a wire that broke at its terminal!-fixed). The diode bridge checks out with the Diode function of the DVM. I do get resistance when I check the stator and rotor windings, but I have no idea if ~3 ohms is a good reading.
While I was in there, I see one of the generator bearings needs replacement.
I made a few attempts to contact the local electric motor repairman, to no avail.
So, it has been on "the back burner" over Winter.
This generator so far has been a money pit, and I'm not interested in searching for, and buying a replacement bearing if the windings are bad.
Do any of you have experience in generator windings?
 

kellys_eye

Jun 25, 2010
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400W for $50???? He didn't see you coming - he must have sent for you!

Money pit. Don't even go there.

Portable (suitcase) inverter generators (with much more stable output very suitable for 'sensitive' electronics) rated at 750W can be bought for $250 new (guessing - it's been a while since I checked). 400W isn't a level of petrol generation I would bother with - a small battery bank with inverter would be a better choice at those levels. Better yet, change all your devices to run directly from 12V DC!
 

Erstwhile

Apr 12, 2022
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400W for $50???? He didn't see you coming - he must have sent for you!

Money pit. Don't even go there.

Portable (suitcase) inverter generators (with much more stable output very suitable for 'sensitive' electronics) rated at 750W can be bought for $250 new (guessing - it's been a while since I checked). 400W isn't a level of petrol generation I would bother with - a small battery bank with inverter would be a better choice at those levels. Better yet, change all your devices to run directly from 12V DC!

Well, the 8 HP horizontal shaft engine is still a nice Consolation Prize!
I already have two 5 KVA gas generators (non-inverter) for standby power, so this one is not essential.
 

Bluejets

Oct 5, 2014
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I have a B&S 5hp here from 1970 ( so 52 years old) and it is 2.5kva.
BTW, your schematic is too small to read anything.
When you uploaded it, did you try to open it to see if you could read it??
 

kellys_eye

Jun 25, 2010
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No, it is 400W (40-50 years old?)
That's astonishing. There haven't been any major advances in electrical generation efficiency AFAIK, nor particular efficiencies in genset motors so coupling a 400W generator with an 8hp motor seems a ludicrous waste of effort and resourse.

I wonder if it's a 'cobbled together' set by someone rather than a genuine manufacturers model?

Anyway, I do watch a lot of generator rebuild 'tubes' with one guy particularly interested in Generac models - perhaps it's one of those?

So, with more web searching I found old generators need to be remagnetized to work properly. So, I followed that procedure, and there was no increase in voltage.

What procedure was that? I've seen the use of an electric hand drill to achieve that but many forget to mention that it doesn't work if you use a drill that has electronic speed controls in it!
 

Bluejets

Oct 5, 2014
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What procedure was that?

Usually involves flashing the fields with a low voltage battery source.
Re-instates the residual magnetism in the core if the system has been standing unused for many years or was subject to any poling of the rotor.

Usually find with these old monsters if the rectifier is ok (usually is) then there will be a shorted turn(turns) in the fields.
Found exactly that fault in an old Dunlite diesel powered unit here a few months ago.
 

kellys_eye

Jun 25, 2010
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I've done the battery procedure myself a couple of times (fixed a few gensets in my time) and not always had issues with the method (I use a small 12V lead-acid cell) but if you have shorted turns the only proper way to test for them is to use a 'growler'.

The 3 ohm reading, if accurate, sounds about right if not a little high.
 

Bluejets

Oct 5, 2014
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but if you have shorted turns the only proper way to test for them is to use a 'growler'.
Or a shorted turns tester....works with alternative dc ac injection.
Used wand growler but one has to disassemble everything.
 

Erstwhile

Apr 12, 2022
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I have a B&S 5hp here from 1970 ( so 52 years old) and it is 2.5kva.
BTW, your schematic is too small to read anything.
When you uploaded it, did you try to open it to see if you could read it??
I did not try to read it after uploading it, I had already printed it out and it is quite readable. The schematic on the "dodgy" website is quite readable too.
 

ramussons

Jun 10, 2014
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Last summer I bought a (very) used 400 watt gasoline powered generator for $50.
The salesman (an auctioneer) said the former owner took "pretty good care of his stuff".
found old generators need to be remagnetized to work properly. So, I followed that procedure, and there was no increase in voltage. ....ent bearing if the windings are bad.
Do any of you have experience in generator windings?
Could you please explain that procedure?
If the residual magnetism is reversed, it can lead to the problem.
 

kellys_eye

Jun 25, 2010
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If you apply a 12V DC supply directly to the slip rings does the AC output voltage change at all? Is the bridge rectifier ok? What about the brushes/slip rings?
 

Erstwhile

Apr 12, 2022
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As the project was put on "the back burner" over Winter, I do not recall which procedure (or two) I used to re-flash the field.
IIRC, one attempt was with an electric drill.
As the weather is warming, I might be getting back into it shortly. But, in the meantime, the vegetable garden will need to be tilled and planted.

P.s. I double checked today, the engine is a Tecumseh HM80 (i.e. 8 HP Horizontal shaft).
P.s. #2 Both the engine and generator are painted (original) Generac orange.
 
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