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Ford 640 idles and runs rough/lack of power

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300 Mag

12-02-2007 18:08:34




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I am having trouble with my '57 Ford 640 tractor. Has the 134 cid gas engine and has been converted to 12v. Choke has to be applied (approx 1/4) to keep engine from stalling at idle, and the engine runs rough at operating rpm's, and has lack of power. Tractor sputters and hesitates when increasing throttle. Carb was just rebuilt after thorough cleaning to remove rust and other junk inside and out. I have made all initial adjustments to carb (main needle out 1 1/4 turns and idle out 1 turn.) Used new gaskets, seats, springs (including the one on the choke door, which was missing prior to rebuild) etc. Fuel supply is sufficient, line is not blocked, fuel streams out at carb. All linkages move freely and controls work properly. I have checked gasket surfaces for leaks and can't find any. I have removed the carb and disassembled/reassembled to make sure there was no debri left from rebuild. Still have the same problem. The really annoying part of this is that before I rebuilt the carb, the tractor ran fine! I rebuil the carb because I had a rust issue and was having to clean the sediment bulb quite often, and the carb was really rusted and full of junk inside, but the tractor ran fine. Makes me wish I had left it alone!!

Could I have the float level incorrect? Is there other adjustments that could need changed? Could the ignition system have a fault that causes this condition? Any help would be greatly appreciated, winter is here and I need my tractor to blade snow!!

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Wagonmaster

12-03-2007 15:49:50




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
I had simular problem with my 640. And Hobby Farm put me onto what might be the problem but I did not see it memtioned in this thread. There is a good possibility that you have some casting flaws that did not rear their head until you cleaned the carburator. On mine I could not stop the carb from leaking fuel and that was the problem. Just a thought!



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300 Mag

12-03-2007 14:49:40




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
I forgot to mention earlier that the carb is a Marvel model TSX-580, based on the tag on the carb screw. Is this the correct carb? I also was wondering how to correctly set the float, the I&T manual says 1/4" from float to gasket surface, but does not say where on the float to measure from. Didn't get a chance today to try any of the suggestions given so far, maybe I'll get a chance tomorrow. I did pull the valve cover and all valves are moving while engine cranks, checked that just to be sure. Thanks to all for the input so far!

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keithr1

12-03-2007 18:03:48




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-03-2007 14:49:40  
yes it is did u get the right kit for it.should be for 600 & 700 1955-1957



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Ed H.-OH

12-03-2007 13:32:41




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
Hello, If thats a marvel carb they may have sold you a kit for a smaller engine that uses less fuel. ( They make that carb for many engines). Compare the holes in the seats with the old ones and espesialy the high speed jet ( under the big adj. screw) If i'm right the holes will be smaller. If so put the old parts back in and it will be fine. Regards -ed



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Kevin Matheson

12-03-2007 09:58:45




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
This may be a long shot, but just this past weekend My 860 would not start. Would try to fire but not enough to keep running. I found out I had gotten water in my oil bath air cleaner and it was frozen solid. No air no run. Cleaned it out, added fresh oil and runs like a top again. Just somthing to look at.



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02

12-02-2007 21:06:33




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
Try adjusting the float level higher.



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keithr1

12-02-2007 19:53:18




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
ok with tractor at operating rpm take the main jet needle turn it in when it begins to stumble back it out till smoothed up..then ur idle u might want to turn the screw on the throttle shaft some..someone else might give u better ideas..hope this helps some



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keithr1

12-02-2007 19:26:49




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 18:08:34  
did u fine tune it when it was running?



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300 Mag

12-02-2007 19:38:27




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 Re: Ford 640 idles and runs rough/lack of power in reply to keithr1, 12-02-2007 19:26:49  
Yes, I made some adjustments to both needles while running, it got a little better but I could not get it running properly.



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old

12-02-2007 21:50:31




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-02-2007 19:38:27  
Ok so you say rebuilt, but. Can you open the main jet to the point you get black smoke?? Can you say open the main jet so far as to pull it out and the engine still run??? If you answer yes to both or either then the carb is not clean enough and you need to try again BTDT many times. These carbs are simple but hard to get as clean as needed

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300 Mag

12-04-2007 13:20:09




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 Re: Ford 640 idles and runs rough/lack of power in reply to old, 12-02-2007 21:50:31  
I opened up the main jet at about 1500 rpm until it was completely unscrewed and tractor ran better, almost like it should. I did not get black smoke at any point, even when unscrewed.



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old

12-04-2007 14:59:57




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 Re: Ford 640 idles and runs rough/lack of power in reply to 300 Mag, 12-04-2007 13:20:09  
Well then you missed something when you did the carb rebuild. So you need to open it back up and clean all the passages real well



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