allis C carb problem
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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=148581
Printed Date: 28 Apr 2025 at 6:32pm
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Topic: allis C carb problem
Posted By: woodsman89
Subject: allis C carb problem
Date 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? |
Replies:
Posted By: steve(ill)
Date Posted: 17 Mar 2018 at 11:04pm
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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. |
Posted By: Steve in NJ
Date 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 |
Posted By: Lon(MN)
Date 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. |
Posted By: woodsman89
Date Posted: 18 Mar 2018 at 2:20pm
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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. |
Posted By: Dick L
Date Posted: 18 Mar 2018 at 4:05pm
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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. |