allis C carb problem

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woodsman89 View Drop Down

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Topic: allis C carb problem
Posted: 17 Mar 2018 at 10:24pm

rebuilt engine and runs nice, but the choke must be on full to make it run. anything less and it dies. Marvel/schebler carb. Had it apart several times cleaned and blew and wired orifices. obviously the idle circuit has issues, tired of taking off and on. any ideas?

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steve(ill) View Drop Down

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Posted: 17 Mar 2018 at 11:04pm

choke on means not enough fuel, or too much air.

---take the fuel line off and run from the tank into a bucket.. do you get full flow ?

---look for air leaks around the intake manifold, or a pin hole / crack in the manifold.

--if its not the fuel TO the carb, and its not leaking air AFTER the carb, then its the carb.. Are you removing the jets and clean inside, or just blowing thru them ? You might want to soak it in a bucket of cleaner for a few hours, then blow out.

Like them all, but love the "B"s.

Steve in NJ View Drop Down

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Posted: 18 Mar 2018 at 9:20am

Follow Steve's directions but if it turns out that its pointing to the Caburetor, blowing out the passages is not enough. As Steve mentioned, jets need to be removed and either the Carb needs a good glassbeading to dislodge some debris or rust or a good soaking in a good vat of Carb cleaner. Running bore brushes through those ports and circuits gets all the muck out of those Carburetors. Don't forget to run a bore brush down the inlet of the Carb also where the 90 degree elbow screw in. Remove that elbow fitting and run a bore brush in that bore and make it shiny. A lot of rust gathers at the back of that cavity and in the unused threads, breaks loose and gets into the Carb causing havoc. That kinda stuff also makes you pull your hair out of your head to... Wacko

Steve@B&B

39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Lon(MN)

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Posted: 18 Mar 2018 at 10:38am

If you haven't already, put new fuel in and don't mix it with any of the old fuel. Start with a clean dry tank.

woodsman89 View Drop Down

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Posted: 18 Mar 2018 at 2:20pm

If you could answer me a question. The metering screw on top, (which has no affect on it), does it meter fuel, or does it meter air to draw fuel?
Is the Marvel or the Zenith the better carb. As I have a Zenith from another C, but it hasn't run in many years. thanks for your help.

Dick L

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Posted: 18 Mar 2018 at 4:05pm

Assuming the carburetor is free and clear of obstructions!
Above idle the idle screw will never have an effect you can hear. If it runs good above idle you can put that screw in your pocket and go to work with the tractor.

The adjustment at the top is the idle air adjustment. When that adjustment does not work your RPM's are faster than what the idle circuit covers. the idle speed is adjusted with the stop screw on the back. That keeps the throttle plate inside from closing. The speed will depend on how much fuel can get past the throttle plate. The idle adjustment mixes air with the fuel to make the engine to run smooth at the stop screw setting. To get a slow idle the stop screw and idle air screw has to be adjusted several times as you slow the engine to just before it wants to die.

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woodsman89 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 17 Mar 2018 Location: iowa Points: 42	Post Options Post Reply Quote woodsman89 Report Post Thanks(0) Quote Reply Topic: allis C carb problem Posted: 17 Mar 2018 at 10:24pm
	rebuilt engine and runs nice, but the choke must be on full to make it run. anything less and it dies. Marvel/schebler carb. Had it apart several times cleaned and blew and wired orifices. obviously the idle circuit has issues, tired of taking off and on. any ideas?

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steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 85545	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 17 Mar 2018 at 11:04pm
	choke on means not enough fuel, or too much air. ---take the fuel line off and run from the tank into a bucket.. do you get full flow ? ---look for air leaks around the intake manifold, or a pin hole / crack in the manifold. --if its not the fuel TO the carb, and its not leaking air AFTER the carb, then its the carb.. Are you removing the jets and clean inside, or just blowing thru them ? You might want to soak it in a bucket of cleaner for a few hours, then blow out.
	Like them all, but love the "B"s.

Steve in NJ Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11925	Post Options Post Reply Quote Steve in NJ Report Post Thanks(0) Quote Reply Posted: 18 Mar 2018 at 9:20am
	Follow Steve's directions but if it turns out that its pointing to the Caburetor, blowing out the passages is not enough. As Steve mentioned, jets need to be removed and either the Carb needs a good glassbeading to dislodge some debris or rust or a good soaking in a good vat of Carb cleaner. Running bore brushes through those ports and circuits gets all the muck out of those Carburetors. Don't forget to run a bore brush down the inlet of the Carb also where the 90 degree elbow screw in. Remove that elbow fitting and run a bore brush in that bore and make it shiny. A lot of rust gathers at the back of that cavity and in the unused threads, breaks loose and gets into the Carb causing havoc. That kinda stuff also makes you pull your hair out of your head to... Steve@B&B
	39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Lon(MN) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 11 Sep 2009 Location: Merrill Wi Points: 2000	Post Options Post Reply Quote Lon(MN) Report Post Thanks(0) Quote Reply Posted: 18 Mar 2018 at 10:38am
	If you haven't already, put new fuel in and don't mix it with any of the old fuel. Start with a clean dry tank.

woodsman89 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 17 Mar 2018 Location: iowa Points: 42	Post Options Post Reply Quote woodsman89 Report Post Thanks(0) Quote Reply Posted: 18 Mar 2018 at 2:20pm
	If you could answer me a question. The metering screw on top, (which has no affect on it), does it meter fuel, or does it meter air to draw fuel? Is the Marvel or the Zenith the better carb. As I have a Zenith from another C, but it hasn't run in many years. thanks for your help.

Dick L Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 12 Sep 2009 Location: Edon Ohio Points: 5087	Post Options Post Reply Quote Dick L Report Post Thanks(0) Quote Reply Posted: 18 Mar 2018 at 4:05pm
	Assuming the carburetor is free and clear of obstructions! Above idle the idle screw will never have an effect you can hear. If it runs good above idle you can put that screw in your pocket and go to work with the tractor. The adjustment at the top is the idle air adjustment. When that adjustment does not work your RPM's are faster than what the idle circuit covers. the idle speed is adjusted with the stop screw on the back. That keeps the throttle plate inside from closing. The speed will depend on how much fuel can get past the throttle plate. The idle adjustment mixes air with the fuel to make the engine to run smooth at the stop screw setting. To get a slow idle the stop screw and idle air screw has to be adjusted several times as you slow the engine to just before it wants to die.