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Harry Ferguson Tractors Discussion Forum
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Carburetor Problems

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Tim H.

11-07-2004 19:06:24




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I have just rebuilt the engine on my 51 ferguson TO-20.I am having problems adjusting the carburetor. I bought a brand new carburetor from this site. It is a marvel shebler copy TSX 361A.My problem is that I can't get it to idle below 500 rpm. When I try to get a slower idle it will not run. I have checked the timing it's right on the money at 7 deg. BTDC. I re-checked the valves they are fine. I have set the carb at the specs listed in the original ferguson shop manuel.1 1/4 on main jet and 7/8 on the idel jet. I checked for vacume leaks and everthing is good at the intake and carb. It acts like it is not pulling enough air at idle. I servised the air cleaner and their are no restrictions. I have also tried another fuel tank. It runs good at higher rpm's and takes full throttle well. Do you think I may have a defective carburetor? Or am I missing something? Any advise you may give would be greatly appreciated.

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John (UK)

11-11-2004 13:25:20




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
Are you sure that the throttle linkage is allowing the carb to go to idle, is it sitting on the slow running stop?



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Vern-MI

11-08-2004 11:18:40




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
Just a guess: Float level to low causing low fuel level in bowl and consequent difficulty with venturi vacuum pulling fuel from the low speed (idle) circuit.



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Tim H.

11-08-2004 09:57:24




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
I should also mention that the governor linkage was disconected while I was making adjustments. I let the engine warm up to operating temp. The idle air adjustment doesn't change the way the engine run's at all. When I back off the idle adjustment screw on the throttle shaft it will start coughing and run so ruff it will die. The manuel say's to make governor adjustments at 400 rpm's. I have tried tweeking it with the adjustment screws. It was a rainy day. Maybe I should try again on a sunny day. Thank you for your help.

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Gerald J.

11-08-2004 11:54:34




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 Re: Carburetor Problems in reply to Tim H., 11-08-2004 09:57:24  
When the idle air has no effect, you are trying to adjust it with the throttle plate too far open. You need to slow the engine as much as possible then adjust the two mixtures until you can get it to idle slowly and where the idle air has effect. Then adjust the main jet under heavy load. They will interact.

When the governor is connected, one can use the throttle position (heading towards closed as optimum) rather than the engine speed as a hint of optimum mixture adjustment.

Gerald J.

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Gerald J.

11-08-2004 09:26:08




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
The book settings are just close enough to get it to run. Then you tweak them until it runs good. Changes with temperature, altitude, and fuel.

The idle mixture screw is probably an air adjustment so turning it in a little might richen the mixture. Readjusting the float level for more fuel in the float bowl richens it over the entire running range.

Gerald J.



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gshadel

11-08-2004 07:00:33




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
Tim, your trouble is probably in the throttle or governor linkages, or the idle stop set screw.
Check for a gap between the idle stop set screw and the carb body while running. If you see no gap, back the set screw out a hair. If you have a gap, need to fiddle with your linkages to let the throttle close all the way. You can try disconnecting the linkages and holding the idle with you hand to see if you get the idle your looking for. Those darn linkages all affect each other, and can be a real pain in the behind to get lined-out. Sounds like you have a manual. Start from the beginning and adjust each linkage like the manual says, don't skip a step.
If/when you get your idle lined out, check you top end RPM's. Sometimes you work so hard to line out the idle that you can over adjust the linkages and lose some top end RPM's.
I find my TO idles a bit smoother around 500 RPM, once you get the idle slowed down, you may find you like it ~500 RPM anyway.
Good Luck

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Volfandt

11-07-2004 19:46:44




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 Re: Carburetor Problems in reply to Tim H., 11-07-2004 19:06:24  
Even tho the manual calls for 400-500 RPM at idle, I set mine for 500. Unless it is different for the Z-120, most all engine manufacturers claim that too low an idle RPM can cause premature crank & rod bear failure.

If you do want to lower it under 500, you may try setting the idle jet to a richer setting.

Good luck
Volfandt



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JJR

11-08-2004 08:26:06




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 Re: Carburetor Problems in reply to Volfandt, 11-07-2004 19:46:44  
While we're talking carbs, what would make the carb start accelerating and decelerating without provocation? My TO 30 was running great for over an hour or so then started lurching without my input on the throttle.



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John (UK)

11-08-2004 11:13:36




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 Re: Carburetor Problems in reply to JJR, 11-08-2004 08:26:06  
It can be the bumper screw adjuster as James UK says or it can be fuel too weak result will be the same. It could be just a temporary weakness of the fuel due to dirt collecting somewhere it may clear itself if you run it harder for a while.You could open the main jet 1/8 of a turn too, that can also clear it, if it does, close it again. The governor bumper adjuster is on the Left side of the timing cover near to the bottom hose, adjust it carefully,have the engine on full throttle and screw it in slightly and see if it improves, if not and you dont feel any resistance on the screw, then the little leaf spring on the inside has broken. If this doesn't cure it watch the governor linkage to the carb at the front end see if there is a lot of play in it. If you need instructions on how to adjust the governor linkage email me at fergusontractors at hotmail dot com telling me what you need.

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James, UK

11-08-2004 09:55:51




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 Re: Carburetor Problems in reply to JJR, 11-08-2004 08:26:06  
JJR, I've had this on my TED - on the Standard engine (so somehwere on the Z series as well) there is a thing called the bumper stop set screw on the timing cover LHS as viewed from the seat - screwing this in VERY SLIGHTLY bit by bit will remove the problem, which is 'hunting' due to the governor being a bit sensitive.

HTH



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