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Generac Generators (SEARS, etc.)

Generac 4000xl running rich and rough


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  #1  
Old 11-01-2012, 02:46 PM
kilabeez0 kilabeez0 is offline
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Default Generac 4000xl running rich and rough

Guy I work with gave me his Generac 4000xl to look at because he said it would run for 10 seconds and shut off. I brought it home and unplugged the low oil sensor and it continued running. I noticed the oil looked thin and dark so I changed it with some fresh 5w 30. Fired it back up still with the low oil sensor unplugged and it runs rough and blows black smoke. I wanted to take the carb off to have a look so I shut the gas off to the unit and let it run dry. Funny thing is, a second after I shut the gas off it ran great until there was no fuel left. I'm sure it's getting too much gas but I'm not sure why. Also it would spit gas out around the carb while it was running so I'm not sure if the needle isn't sitting in the seat all the way. Carb looked clean and the gas was fresh gas from a small mom and pop store that sells Sunoco and the pumps had been filled that morning.

If I push the idler arm on the top of the motor back simulating no load and low idle it seems to run ok, but as soon as it loads up and the rpm's climb it runs terrible blowing black smoke. I read this post which seemed to be the same situation http://www.smokstak.com/forum/showthread.php?t=106598

I'll check the valve clearances tonight or tomorrow and report back. I'll also change the plug. If that doesn't work, what should I do next? Thanks
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  #2  
Old 11-01-2012, 03:55 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

Three things:

One: its spitting gas out of the air cleaner because the carb float is not pushing the pin valve to close the fuel line. The risk is if it doesnt leak out of the air cleaner, it leaks into the crank case, causes hydrolock in the cylinder, and gets in the engine oil. THIS MUST BE ADDRESSED FIRST to prevent potential engine damage. The oil pressure sensor failure is a common problem, it must be replaced, just do not remove the 2nd nut. connect the wires between the two nuts that are provided.

Two: The black smoke from exhaust is engine running rich, so its a fuel delivery. Observe the main jet inside the fuel bowl. If it was drilled out this would explain it running rich. Also if its a Nikki carb there should be a rubber stopper in the idle circuit next to the main jet. If this is missing this may explain the engine running rich if the main jet is not compromised. Change out the spark plug after you address the carb issues

Three: Adjusting the valves is a must, adjust according to the owners manual specs. Commonly, these engines are adjusted with the cylinder TDC ON THE COMPRESSION STROKE! Exhaust valve is used for compression release not intake.

Hope this helps, read some of my threads, directly dealt with EVERY issue you are having now, with great success in having a smooth running machine with the reources available on Smokstak.

BTW: Welcome to the forums!
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  #3  
Old 11-01-2012, 07:23 PM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

Ok I adjusted the valves but they weren't that bad to begin with. Put a new plug in, old one was BLACK. That didn't help. I know the needle isn't sitting in the seat and its a pladtic float so there is no adjustment. Ill look for the rubber piece in the carb. I doubt the previous owner drilled out the main.

Last can I just leave the oil sensor unplugged? You said it needs to be fixed, but why? Reading your reply I don't know if you mean to replace it or tie the wires together and eliminate it? Thank you for your help so far.

---------- Post added at 07:23 PM ---------- Previous post was at 07:20 PM ----------

O I forgot to say it only runs like this when I turn the auto idle control on and put a load on it. When I remove the load and it isles down at low rpm it runs fine.
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Old 11-01-2012, 08:48 PM
RSCurtis RSCurtis is offline
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Default Re: Generac 4000xl running rich and rough

That would indicate the float system is OK. Bassplayer is probably on target with the rubber plug.
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Old 11-01-2012, 09:05 PM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

Any pictures of this rubber piece? Is it something I can purchase separately if its missing? And what is the purpose of this piece? Thank you
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Old 11-01-2012, 09:19 PM
tinkerman2012 tinkerman2012 is offline
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Default Re: Generac 4000xl running rich and rough

Exactly what was wrong with the 6500 I'm working on. The rubber plug was missing. I made another from an "O" ring and it was of my own making. The engine hadn't run in at least ten years and carb was such a mess you had to actually force the throttle and choke levers. When I cleaned it up I must have misplaced the plug. Anyway, problem solved.
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Old 11-01-2012, 10:50 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

here is the plug you can buy.

http://www.amazon.com/BRIGGS-AND-STRATTON-694924-PLUG-CARBURETOR/dp/B005F6PV8A

If you use an o-ring, i tried this, it must be a Viton plug as it can tolerate gasoline. Jam it in there, and it will work.


Far as a main jet, I will refer to my last thread for my carb rebuild. Vendors DO sell individual parts separately as replacements, but Nikki carbs are hard to find individual parts. You would have to get real lucky with a diagram of that model carb showing that exact part# for it. Best of luck.

http://www.smokstak.com/forum/showthread.php?t=98499

This is a picture of a kit that has the black rubber plug

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  #8  
Old 11-02-2012, 12:07 AM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

Wow great info thanks! So why can't the top of that passage just be sealed off with jb weld or something of that nature? Why does it have to be a rubber plug? Actually why didn't they just seal it off from the factory?
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  #9  
Old 11-02-2012, 12:48 AM
len k len k is offline
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Default Re: Generac 4000xl running rich and rough

My Onan (with a Nikke ?? carb) that looks similar to the pictures, uses a small ball bearing press fit into that area to seal , I believe.
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Old 11-02-2012, 08:34 AM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

after speaking with the owner he said that when the oil switch went bad he dropped the carb bowl thinking it was a carb issue. He said he actually saw the rubber plug on the ground and tossed it thinking it had nothing to do with it. Problem solved!!! Thank you so much for the help! One last thing, I'm going to replace that part and see if that fixes the fuel spitting issue. If not I'll do the needle and seat. Any tips on where I can get a carb kit for this carb? I didn't have much luck on ebay which usually has EVERYTHING.
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  #11  
Old 11-02-2012, 09:06 AM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

Quote:
Originally Posted by kilabeez0 View Post
Wow great info thanks! So why can't the top of that passage just be sealed off with jb weld or something of that nature? Why does it have to be a rubber plug? Actually why didn't they just seal it off from the factory?
I asked that myself, but my guess is the same carb was used for multiple engines and they needed a way to adjust the fuel mixture depending on the engine, ever since the EPA fixed the idle mixture to a set value.

What is the part# for your carb? The 4000EXL and 7000EXL used different model carbs, but the replacement parts were all standard size and compatable with each other, with exception to the main jet and mixture settings. The fittings were all the same. The rebuild kit below comes with everything you need that wears inside the carb (including a new pin valve except for that rubber plug, but I already provided that part# for you.

http://www.partsfortechs.com/asapcar...562-p-940.html
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  #12  
Old 11-02-2012, 09:47 AM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

Im not sure the model number of my carb. Where would I find it? The one I'm working on isn't an EXL it's the XL. Honestly I think I'm going to just try some gas tank repair expoxy and just block off that hole at the top. So the link to the kit you just sent me is for the 7000exl not the one I might need? Thank you
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  #13  
Old 11-02-2012, 10:04 AM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

Yes but the parts should be identical. Thee is another thread with someone with a 4000EXL and the same rebuild kit worked for his carb. The model number should be stamped on the side of the carb body, or in your manual
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  #14  
Old 11-02-2012, 12:09 PM
len k len k is offline
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Default Re: Generac 4000xl running rich and rough

Since it runs good on idle, the float and needle valve are workig properly, and don't need replacement. Shake the float , if there is no gas inside, I would just put it back in.
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Old 11-02-2012, 02:47 PM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

anyone see any problem with sealing that off with some gas tank repair metal epoxy?
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Old 11-02-2012, 02:58 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

that epoxy is resistant to gas but not bulletproof. a viton o ring plug is better
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Old 11-02-2012, 03:26 PM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

how do u know if it is viton? and how do u know the piece will stay in there and not just fall out?
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Old 11-02-2012, 03:29 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Generac 4000xl running rich and rough

it will say Viton on the box, and using a small needle or flat screwdriver to jam it in there. Its not under any serious pressure, its designed to plug the idle circuit which is fed by the main jet. If left unplugged, the idle circuit and main circuit are overfeeding the emulsion tube with gas thus your rich running engine. plugging the idle circuit allows the main jet to meter the amount of gas going in the emulsion tube out to the carb.
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Old 11-02-2012, 03:31 PM
kilabeez0 kilabeez0 is offline
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Default Re: Generac 4000xl running rich and rough

hmm usually hardware stores dont sell o rings in boxes, they just have them in baggies or a bunch of them in a container. like ace hardware.
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Old 11-02-2012, 03:48 PM
len k len k is offline
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Default Re: Generac 4000xl running rich and rough

If you go to an industrial supply house, nike for bearings they will usually sell o-rings.

Here's a supplier of o-rings that shows a chemical compatability chart of different o-ring materials with various chemicals,,,,,,, gasoline is a few pages down.
http://www.marcorubber.com/compatibility.htm

In a pinch I suppose you could always take a razor and cut a small peice of a car tire and cut it into a roundish shape and ram it in there.
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