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Adjusting Carb

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Jeff

06-19-2003 17:08:04




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I was trying to adjust the carb on my 50 JD A and I am not getting it right. Do you have to have the throttle all the way closed to set the idle needle. Any help or tips would be greatly appreciated. Thanks




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ChuckW

06-20-2003 10:54:57




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 Re: Adjusting Carb in reply to Jeff, 06-19-2003 17:08:04  
it's been my experience if you blame to much on carb settings the problem is elsewhere...generally if your tractor is in good shape, it should run okay at factory settings...if not your passages are probably clogged.



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Clooney

06-19-2003 18:59:26




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 Re: Adjusting Carb in reply to Jeff, 06-19-2003 17:08:04  
Jeff, you do not necessarily want the throttle all the way closed. You want the engine at it's rated idle speed. [that will be close to a closed throttle plate though]. On those DLTX carbs they tend to go a little rich as the idle speed gets real low due to low air flow & poor metering & if you set the idle mixture at too low an idle it will be off at the regular rated idle speed.
~To properly set the idle the tractor must be hot & the choke plate must be all the way open. ~If you still can't get the idle set correctly make sure the throttle shaft bushings aren't excessively worn & pull the carb & verify that the throttle plate is centered & isn't worn on the ends [a common problem]. If the air gets by the end of the throttle plate the idle metering goes crazy..
~If it still won't adjust correctly make sure the idle needle doesn't have a worn ring in it's tip & the float is set to the correct height.
~If you still have idle problems then suspect a plugged idle passage or transfer hole. If turning the idle mixture screw all the in or all the way out won't adversely effect the idle you probably have a plugged idle passage or port.
~A good place to start your idle adjustment is 2 turns out from seated & once warm & near the correct idle speed slowly turn it in until you the idle roughens up a little then back it out slightly until it smoothes out again...

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John T (Long Post)

06-19-2003 17:53:21




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 Re: Adjusting Carb in reply to Jeff, 06-19-2003 17:08:04  
Jeff, Yes, you have to have her at idle to set that idle needle. The initial basic rough in settings are closed then 3/4 to 1 turn out for the load needle and closed then 1 3/4 to 2 out for the idle needle.

What is it youre not getting right????? Whats it doing wrong???? Wont she idle down slow and smooth??? Does it take gas (not cough or sputter when you suddenly open throttle) and run okay under load, or is it only idle youre having problems with??? Does she throw black smoke out the stack at idle??? Does any amount of choking make her run better???? Does the RPM surge up n down up n down when youre at idle???? i.e. does she sit there and lope up n down. Does any blue smoke come out the stack??? These questions will help me further diagnose your problem!!!!! !!!!! !!!

CARBURETOR

1) If she wont idle down nice and slow and smooth, first try removing the governor linkage there at the carb, and see if by hand you can hold the throttle to where she idles down slow and smooth??? If you can manually, the governor linkage may need adjusted or the governor may have a problem, post back what happens!!!!! !!!!! !!!!! !!

Is the lil sprign post catching the idle adjuster screw and holding it back some?????

2) If she wont idle smooth even with the governor disconnected (you cant manually hold her to a good idle) and adjustign the idle needle dont help, proceed below:

3) A common cause of poor idle is vacuum leaks, usually past the throttle bushings cuz they are worn and sucking in air, or the manifold is leaking. Use WD40 or Carb Cleaner or an unlit propane torch sprayed at the carb and its throttle shaft and around the base of the manifold at idle, and if you find a place that mekes her speed up and idle better, theres a vacuum leak there.

4) If theres no vacuum leaks and the governor is okay and no adjustments make her idle okay, you may have some clogegd idle circuit passages inside the carb. If thats the case post back, cuz its a fairly long winded and detailed procedure I can advise you with, but no use to post all that now.

IGNITION

Is it a magneto or battery powered ignition??? What type of mag???? Have you any idea where the start or run timing is set at??? How old or dirty or fouled are the plugs???

Inspect and clean and gap the plugs, be sure you have wire core, NOT automotive carbon suppressor type wire. Insure BOTH plugs are producing a good visible BLUE spark, not a faint thin wimpy yellow one. Check the points gap and be sure they are clean. If only gray oxide coated but otherwise smooth, clean/polish them but if burned or pitted or carboned up, replace them.

These are a few startign points, once I get more info from you, I can better advise you. Let me know whats wrong or what you discover.

Good Luck n God Bless

John T Nordhoff in Indiana

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WjW

06-19-2003 17:20:41




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 Re: Adjusting Carb in reply to Jeff, 06-19-2003 17:08:04  
I do not have any experiance with the a but normally you must have the machine at an idle to adjust the idle screws as this is when they are affecting the carberator. at higher engine operation the idle jets are not controlling the fuel any more. this is my basic understanding.



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