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JD 50 carb question

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Mike C.

01-13-2002 00:25:20




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The load needle adjustment on my 50 seems to have little if any effect. I have to set my idle needles
very rich in order for it to run ok at higher speeds, otherwise it starves for fuel. Especially
below about 1/3 throttle. At half throttle or more it seems to smooth out some. I have tried load needle adjustment from 2 to 5 turns with no obvious
difference.

I am going to pull carb and go into it and would appreciate any suggestions on what to look for.

Mike C.

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Clooney

01-13-2002 07:14:42




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 Re: JD 50 carb question in reply to Mike C., 01-13-2002 00:25:20  
~Mike, I presume you have a dual DLTX as you are talking "idle needles". You might have to define your problem a little more to figure exactly out where your problem lies.
~One thing to understand on the dual DLTX carb is the "load needle" is actually a (fine tuner), the load metering is handled by fixed jets & the single needle is just for economy & load variations. The other thing is that at 1/3 throttle & down the load system isn't utilized, most if not all of the fuel metering is done by the idle system, & the load system doesn't come into play until more throttle opening due to higher load or acceleration.
~The DLTX has a complicated idle system that utilizes long passages drilled adjacent to the main bores & those intersect passages drilled into the main well. Because your tractor seems to idle, it doesn't sound like the main passage(s) are completely plugged, so fuel is at least getting to the #1 idle orifice, given the information you have furnished it sounds more like your problem is in the 2nd or 3rd idle orifice(s). Those 2 orifices are on the high pressure side of the closed throttle plates & add air to the idle mixture at slow idle conditions, as the throttle plates are opened farther the 2nd & 3rd idle orifice(s) are moved into the low pressure side of the throttle plate(s) & quit supplying air to the idle mixture & start supplying fuel to the air traveling past the open throttle plate(s), that would probably be in the 1/8-1/4 throttle opening region. As the throttle is opened farther due to more load, the main nozzles start to supply more of the fuel & the metering moves towards the venturi & main nozzle area of the carb, at this time the fuel metering is being handled by the main jets & nozzles & being attenuated by the load needle. ~You might be able to pull & clean the main nozzles, make sure the load needle floating sleeve is free to float, clean the main jets & work a small wire into the 1st. 2nd & 3rd idle orifices to cure your problem. If that doesn't do the trick you will probably have to pull those pesky little hardened balls in the throttle plate ends of the passages. If it gets to that post back or E-Mail me.

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Mike C.

01-13-2002 13:11:12




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 Re: Re: JD 50 carb question in reply to Clooney, 01-13-2002 07:14:42  
Thanks for the reply. It sounds like some of these orifices may be clogged.

To be more specific, I have to adjust my carb very rich at slow idle (plenty of black smoke) in order to get it to run right up to about 1/4 - 1/3 throttle.
If I lean it out at slow idle (no smoke) it idles great, but if I open the throttle even 1/8 it will begin to starve for fuel and may even die. It seems if I get it on past about 1/3 throttle it runs ok.

Mike C.

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Clooney

01-13-2002 13:36:48




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 Re: Re: Re: JD 50 carb question in reply to Mike C., 01-13-2002 13:11:12  
~Mike, how slow of an idle are you talking about? On most DLTX carbs if the idle mixture is set at 600 RPM's (the factory low idle) they will puff a little black smoke at 300-400 RPM's if the needles aren't reset leaner to idle at that speed, then they will be a little lean at light throttle openings.
~You were talking about 5 turns out, that is too far & usually indicates a problem.
~Because you are having problems at off idle & not at slow idle or above 1/3 throttle it sure sounds like 2nd & or 3rd idle orifices are the problem.
~Make sure your bowl vent isn't partially plugged & the baffle(s) are open & that the bowl base gasket isn't leaking & allowing the bowl to vent to atmosphere outside of the air filter, it needs to vent to the same atmospheric pressure as intake between the air filter carburetor to allow the carb to meter correctly.
~Be careful when cleaning any holes & orifices in the idle circuits, if you enlarge the orifices you will have a difficult time getting the carb to meter correctly at all speeds & end up with the same problem you have now.

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Mike C.

01-13-2002 19:02:49




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 Re: Re: Re: Re: JD 50 carb question in reply to Clooney, 01-13-2002 13:36:48  
I'm not sure what speed the idle is set at as I have no way to measure RPM. It's idling right at the point the timing retards but I'm not sure what speed
this is.

Mike C.



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