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Help? My JD A runs rough

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Charlie

04-25-2000 16:46:38




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I have a late model A that runs like it is starving for gas, revs up and down up and down an will not hold a steady idel. I cleaned carb 3 or 4 times and put in a new float set 3/8 below the top of the bowel and blew compressed air through all the passages, but still I can not get the engine tu smooth out.

What is really strange is th idle screw seems to have no affect what so ever. I can close it right down and nothing happens,,,or I can open it completely. No matter what I do,,,the idle screw seems to have no affect on the idle.

when i adjust the load screw,,,i can not get the engine to smooth out iether,,,always it is rough like it is starving. But if i tighten down the load screw completely, the engine will stall.

The electrical systems is good,,,it has new points and plugs and starts every time.

The tractor sat all winter and last year it ran perfect.

Can anyone give me a clue what could be wrong.

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John T again

04-26-2000 09:32:57




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 Re: Help? My JD A runs rough in reply to Charlie, 04-25-2000 16:46:38  
Charlie, I used to heat gently the cast around the drill plugs and they always came out easy when hot and use a good sharp proper sized screwdriver. However, Roberts Carb Repairs, who has forgot more carbs then I ever seen, says to heat the drill plug itself easy just till you see a slight color change, let then cool, then remove them. Regardless, heat does the trick. Regarding cleaning, I used Mig Welding Wire and torch cleaner tips, but Paul bought the extra long 40 and 53 drill bits from Roberts at Gathering of the Green so we can do it right now. Ol John T in Indiana PS I believe there are three plugs and two are 40 bit size and other one is 53.

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John T

04-25-2000 20:33:46




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 Re: Help? My JD A runs rough in reply to Charlie, 04-25-2000 16:46:38  
Charlie, if she wont idle down cause the idle circuit passages are clogged, the governor opens up where the power jet kicks in, then she slows back down, and repeats the process over and over. The only way to fix is is to clean all the idle circuit passages by removing every brass screw drill plug and cleaning out the passages with torch cleaner tips and Mig Welding wire and finally No 40 and 53 drill bits. You can boil it out and soak in gumout till the cows come home and it will never clean the idle circuit passages till you remove all the drill plugs. Been there done that and got the T shirt and Paul even bought the extra long 40 and 53 drill bits from Roberts. Then she will idle properly. Also, if shes sucking air and has a vacuum leak, usually due to worn throttle shaft bushings, she runs lean and you cant get enough gas through her at idle to compensate which also causes a poor idle. Ol John T in Indiana PS This assumes your ignition is in proper condition.

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Joe Woodson

04-25-2000 17:53:52




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 Re: Help? My JD A runs rough in reply to Charlie, 04-25-2000 16:46:38  
Your problem sounds exactly like the problem I am having with my Model 40. It will not idle and the adjustments have no effect. I pulled the spark plugs and they were very "sooty". I was wondering if your JD A and my Model 40 might have the same type of carb and if the clooney's suggestions would work on mine. My neighbor suggested the same thing (debris in the carb). Thanks.



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clooney

04-25-2000 18:22:55




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 Re: Re: Help? My JD A runs rough in reply to Joe Woodson, 04-25-2000 17:53:52  
Joe, your 40 has a Marvel-Schebler TSX carb on it. That is an "up-draft" carb. The principal is the same but the passages & orifices are different. The tsx has a little orifice in the side of the throttle bore (just about even with the throttle shaft) that likes to gum up. You should be very careful running wires or drills in the orifices in that carb. If you do, use only soft wire. I usually pull those carbs apart & soak them in carb cleaner first. If that doesn't do the trick then I go after them with a soft wire. I have had some luck reving the engine then placing my hand over the air intake on the carb, that will pull gasoline up through the idle & air bleeds & "sometimes wash the dirt or gum out" Be very careful removing the "L" shaped air intake hose, those things are made of "unobtainum".

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Joe Woodson

04-26-2000 19:23:19




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 Re: Re: Re: Help? My JD A runs rough in reply to clooney, 04-25-2000 18:22:55  
clooney, Thanks for the info. I hope to tinker with it this weekend. The only part that concerns me is that in the process of trying to adjust out the rough idle (I was having the same problems as Charlie) that I have the slow idle and load screws thrown way off. After I tear the carb down for cleaning and put it back together is there a good initial adjustment to start out with on the idle and load screws? Thanks.

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clooney

04-25-2000 17:28:42




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 Re: Help? My JD A runs rough in reply to Charlie, 04-25-2000 16:46:38  
Charlie, it sounds like you have a piece of dirt or rust in the idle circuit. Those old cast iron carbs are real hard to get the idle circuits clean. You will probably have to pull the little brass plugs & run a wire or small drill bit through them. If you are handy at working on carbs & mechanical things there should be no problem. The "experts" will tell you that you should run the proper sized drill bits through the circuits, but I have had good luck just using a small stiff wire. There are a couple of small holes in the throttle bore, usually 1 in ft.of & 2-3 behind the throttle plate, these holes are quite small & hard to see without pulling the throttle plate. There is a small brass screw right accross from them to allow you get a small wire in there. There is also a brass screw that you access through a hole in the ft. mounting flange, remove it & run a wire through there. If you blow compressed air in the carb, remove the float bowl first or you take the chance of collapsing the float. The best way to verify a carb problem is to substitute a "known good carb from another tractor" sometimes running the tractor with the choke half on will also help you define a carb problem.

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Charlie

04-26-2000 06:50:26




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 Re: Re: Help? My JD A runs rough in reply to clooney, 04-25-2000 17:28:42  

Thanks for all the help. I did run the choke and it runs a little better, i believe the problem is in the passages. The only problem is two of the screws will not come out. One on the stem near the bowel is,,,and the other on the front by the thrttole plate. This afternoon i am going take it to a machine shop to see if they can drill them out and retap them.

Also,,,what kind of wire do i use to clean the passages,,and where can I get it.

How bad does the throttle plat bushing have to be worn to cause problemas? Mine feels like a snug fit.

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