Zenith tuning problems.

[john w]

 I  have fitted new Zenith  carby [copy] in place of Solex to my series 2a but having troubles getting it to run smoothly. Main problem is motor 'stumbling' when accelerating, at any speed.  Experience, from another age, with Holden Stromberg carbys suggests the accelerator pump is not functioning properly. This one only pumps out intermittent fuel stream when observing, being hand operated. The pump is a metal piston inside the usual cylinder, but has no plunger seal on the piston, as does the Stromberg. The piston has three grooves  around its circumference. Should there be O ring seals in these grooves? 
  Idles OK , cruises OK  starts OK [not like Solex]
   Also needs choke for long time when cold. Choking does overcome the accelerator 'stumble' 
  I considered the main jet may need enlarging, [ is stamped 125] but engine seems to pull OK under max throttle [or as well as can be expected, no great ball of fire]
  Past carby experience suggest the enrichment jet may be faulty perhaps?  Have completely dismantled the carby and blown out with compressed air.
 

[Philthy]

Don’t mean to sound negative but knockoff Carb’s aren’t worth the trouble regardless of what its running.

Better off buying a cheap ultrasound cleaner and rebuild the old one if you can.

Never seen one work properly.   

[tona]

   G/AY john w , just a thought ,  are you getting a good squirt when the acc is put down, check this when engine is stopped , no fuel ,no go properly , as you say it may want  a pint instead of a schooner, just a   thought,TONA,.