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Subject: 8N Carburetor

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Cal Sexsmith    Posted 05-11-2022 at 19:04:43 [URL] [DELETE]        [Reply] [Email]  
  • 8N Carburetor
  • Recently my 8N has been stalling after running for about 10 minutes. After waiting a couple of minutes it will re-start and run another 10. Acting very much like fuel starvation. If I take the fuel line off of the carburetor and open the sediment bowl valve I get a steady stream of fuel. However, if I instead remove the plug from the carburetor float bowl I get an initial steady flow then it slows to a trickle and sometimes stops. If I put the plug back in and wait a couple of minutes then remove it again I get an initial steady flow followed by a trickle.

    My assumption was a problem with the needle valve or the floats. I took off the carburetor, opened it up and all seemed OK although the needle valve appeared to stick a bit at times. This is a replacement carburetor about 5 years ago. I still had the old Marvel Schleiber carburetor so I opened it up with the thought of stealing some parts. I noticed that the M&S carburetor has a small piece of wire connecting the float to the needle valve and when the float goes down it pulls open the needle valve. This wire is not on the new carburetor. Could this be my problem?

    Den N Ms    Posted 06-10-2022 at 22:25:41 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N Carburetor
  • Cal Sexsmith , Remove and check the screen behind the inlet elbow.It could be choked up with crud causing slow fuel flow.Clean it out with some carb cleaner and inside the carburetor inlet.

    Ed Gooding (VA)    Posted 05-15-2022 at 09:15:38 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N Carburetor
  • If you want to learn a neat way to check if your float level is correct without disassembling your carb, click the link below for a quick how-to from member Dave Smith.

    Jim    Posted 05-13-2022 at 06:18:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N Carburetor
  • Your OEM Marvel-Schebler carb can be rebuilt over and over. New aftermarket models tend to be junkers. Some time ago somebody decided to re-invent the wheel and came up with new needle & float valve that now used a clip and controlled the float that way. Why add more parts to a system that worked perfectly fine otherwise? Some say it is a better design, but that is strictly opinion, not fact. New needles usually now use a Viton tipped needle, again, why? Your MS carb was replaced with the new style. The needle & valve are not your problem if you set the float level to at the closest point, use a drill or dowel as a gage. First thing is to perform the Fuel Flow Test. Chances are the problem is upstream of the system. TISCO makes the best carb rebuild kit. Use a brass venturii and float.




    Ed Gooding (VA)    Posted 05-11-2022 at 19:36:41 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N Carburetor
  • Cal, check your email.

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