Zenith 62M 63M 263M Troubleshooting


As I see it, one of six possibilities exist (in no particular order): 

  1. Viton needle tip not cleaned with non-residual carb cleaner so as to be compatible with gasohol.
  2. Fuel quality so poor that needle won’t seal. It sounds as though fuel is rusty, which suggests water is present, which suggests that the gasoline and ethanol have separated — you get the picture.
  3. Debris stuck in needle seat holding needle open. Did he assemble the fuel system with teflon thread tape? I bet he did.
  4. Float is leaking.
  5. Fuel pump is generating more pressure than owner has measured. In my opinion, 5 – 6 PSI itself is too much for that carb, and is certainly more than a 4-cyl. engine requires.
  6. Needle seat threads were not dressed with teflon thread paste, and fuel is leaking past them.
Updated on 12/15/2020

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