Marvel Sheb carb jet question

Also check for air leaks downstream of the fuel metering system of the carb. They lean the mixture out and require running with the choke out with a good ignition system. You said that the throttle shaft was well worn. That's one source. The gaskets between the intake manifold and the carb andbetween the intake manifold and the head, and the intake manifold itself can be other leakage sources that lean out the carb mixture.

The idle mix screw only is in effect up to ~400-500 rpm, then the main power mix adjust screw (big screw) takes over.

In addition to fix'in-up your carb., I highly recommend you pull a plug and check your spark. You should get a fat blue spark, not a weak orange spark. Poor running is often associated with poor spark... just like on the N.

There is indeed suppose to be a idle jet... I don't know if it is the same ID as the one from a N, or not.
At this point, you might want to spend the ~$15 or so and get a rebuild kit and fix that carb. The float gap should be 1/4" when you re-assmble. FErgys are prone to flooding the carb when the engine is off for an extended period, just like a N, so make sure your fuel shut-off is working good.... in fact, it is the exact same shutoff as a N or Jubilee... Keep us updated.

George

I got tired of the fuel shutoffs leaking on my 2 Ns so I rigged this up. I removed the mesh screen from a stock elbo. Drilled out the id of the valve and soldered back in the screen. Cut the fuel line and used the compression fitting that came with the valve. Problem solved. I only use the brass shut off when parking for the winter or putting away on Sunday night etc. I've been through probably 4 fuel shutoff valves to get 2 that work right. I still can shut them off, pull the fuel lne and drip..... ..... ..... drip..... ..... ....Drip