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05-30-2001 12:55:13

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Many thanks to all for your suggestions, however, (unfortunately) none of them seemed to have any impact on eliminating the problem. To recap, I have a recently acquired 1952 8N that produces black exhaust smoke and rich fuel smell at any throttle setting below approximately ĹÖit still smells rich at full throttle, but you donít notice the smoke very much. I purchased and installed a brand new carb, which didnít help at all, in fact the tractor behaves just as it did with the old carb (adjusting the idle air and fuel mixture screws in or out on either carb seem to have little effect). Per your suggestions, Iíve completed a tune-up with new plugs, points, (set to I&T FO4 specs) rotor, condenser, and distributor cap, and completely cleaned out the air cleaner (it wasnít dirty at all, the oil bath was very clean). Still no improvement. I next began to suspect the 12-volt conversion and some problem related to that modification and the coil. I have the side-mount distributor and automotive type coil, along with the standard ballast resistor, and seem to get a nice blue spark at the plugs if I pull the plug wires off one at a time with the engine running.
Iím still puzzled by the fact that the engine seems to smooth right out, stop smoking, and actually idle faster if I turn off the after-market in-line fuel shut-off valve near the carb (until it runs out of gas), which makes no sense to me at all. That behavior would indicate that the fuel pressure is overriding the fuel needle and seat in the carb, overfilling the carb fuel bowl and causing the rich condition, but how can that be with a gravity feed fuel system?? Arenít all N tractors gravity fed their fuel? Is there some sort of fuel volume limiting device in the original fuel line and/or valve that is missing on my tractor, and that could be the source of the problem? I did note that the fuel valve mounted on the gas tank seems to have been modified somewhat (there is no shut-off knob on it, and it has what looks like a second line coming out of it that has been cut off and crimped closed, along with a fuel line that runs between the top of the engine and bottom of the fuel tank, then takes a 90 degree turn downward to connect to a piece of rubber fuel hose, fuel filter, another piece of fuel hose, plastic fuel cut-off valve, and another piece of hose to connect to the metal fuel inlet tubing on the carb).
Iím really baffled by this problem, and I know this is a long-winded post, but I wanted to provide as much information as possible to see if any of you N experts out there have ever had this problem, and how you corrected it.
Sincere appreciation in advance for any help you can offer.

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05-30-2001 23:22:06

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
You've certainly covered all the basses and until this update it was certainly a mystery to me. But now that you have revealed the fact that you have various rubber hoses and aftermarket fuel filters in line (as well as the questionable shutoff at the tank), I think you have also revealed the source of your troubles. Rubber lines can deterioriate internally and cause blockage under pressure. When the pressure is relieved somewhat, fuel is again allowed to flow. I'd replace the shut off with the proper unit and install a metal fuel line from there to the carb.

Hope this helps.

Mountainman (CA)

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Dell (WA)

05-30-2001 16:09:25

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
madjak..... everyone's offered some excellent advice, howsomever...no where do I read that you checked your new carb float level, I'm sure you must have, being as through as you've explained, but...has classic symptoms of high carb float..... .Dell

Oh yeah, I don't believe your problem has anything to do with being converted to 12 volts

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05-30-2001 17:55:04

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 Re: Re: PROBLEM STILL THERE...HELP in reply to Dell (WA), 05-30-2001 16:09:25  
Sorry Dell, I forgot to include that info in my post, but I did check the float height on the new carb, per your suggestion, and it is correct (as is the float height on the old carb). Also agree with your assesement that the 12 volt conversion is not to blame, the "sparkies" is too good!


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05-30-2001 13:14:08

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
Nice post, but wow. You've done just about everything. The gas is gravity fed, so I don't think the fuel valve or lines have anything to do with the problem. But try this..... just a thought, but it almost sounds like you are choking the engine all the time. Is the choke rod not hanging up causing the choke to be partially closed ? Also, and this is really a guess, pull the air cleaner tube completely off the carb inlet (I know you said you cleaned it, but I'm just looking for straws now). Any difference ? Finally, and just another guess, do you have good gas. I once had diesel mixed in with a load of gas and it kind of acted the same way. The only other guess I would have is to re-check your timing and ignition wires to make sure they are in proper sequence. Hopefully, the other experts on this Baord will have some better ideas than my fumbling around. My $.02

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Possible Fire Hazard? (ED - Illinois)

05-30-2001 14:11:15

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 Re: Re: PROBLEM STILL THERE...HELP in reply to TimK, 05-30-2001 13:14:08  
Not to step on your toes Tim, but I seem to remember a post from ZANE a long time ago where he cautioned against removing the air cleaner tube from the carb because it is a fire hazard.

Anyone else remember this?

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05-30-2001 13:09:44

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
This carb is limited in its ability to shut off fuel at the float, hence the cut off valve beneath the tank. You may be able to solve the problem by removing all the fuel lines, replace the cutoff valve in the tank with the proper unit, install a new fuel line,( You can get a 1/4/" by 24" steel brake line, put an "S" bend in it under the tank and use both fittings without cutting the line)and reset the float with a 7mm or a 9/32 drill bit for a gage. Be sure the bowl gasket is in place when you adjust the float. If you set the float too low the engine will starve for fuel under load. Hope this helps, did mine this way.

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05-30-2001 14:31:42

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 Re: Re: PROBLEM STILL THERE...HELP in reply to RB (VA), 05-30-2001 13:09:44  
I agree with RB.

Get the right shutoff and a full length steel line.
Sounds like your line is oversized and it could be that you are gravity feeding a column of fuel to the carb that may be too big.
The float may not be able to shut out the pressure?

Just a thought...

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Danny in CO

05-30-2001 13:08:49

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
Have you checked to see if you might have a leak around the intake/exhaust manifold? Use some WD40 and spray around the manifold. If the engine smooths out, you have a leak. If so, it could be just a gasket. Or you may have to replace the manifold. You may need to pull the manifold and look for holes between intake and exhaust ports.

This is just a guess.

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05-30-2001 13:04:40

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 Re: PROBLEM STILL THERE...HELP in reply to MADJAK, 05-30-2001 12:55:13  
I would check/ replace the float needle and valve. It is probably leaking causing the rich condition. Shutting off the fuel with the valve kinda proves that. albe

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