From:Dave Molnar
Subject:RE: RE: RE: Zenith T4X jets Date:Sat Sep 22 16:30:53 2012
Response to:4269
In some of my research regarding jets, I have read that the hole size although one of the factors is not the only thing to consider. It sounds simple enough to just drill the jet out to your favorite pin gauge size but that is not all. It depends more on "flow" rather than jet size. Drills generally leave a very rough hole. A smoother reamed hole and a drilled hole will have very different flow rates. There are many times also small chamfers on the back side of the hole that affect flow by design. From what I understand it is more important to match the flow rate of a jet. Perhaps I'm spitting hairs but but worth mentioning.

You can also fill the jets with solder and redrill for a smaller size. This is how I was able to fit a glass bowl Ford carburetor onto my Crosley powered motorcycle. It's takes some trial and error but you can narrow it down to the proper size. Many miles on this bike without a problem.

Keep in mind those jets are the same as used on many car Zenith carbs and can easily be re-drilled to increased sizes to find the one suitable for your Henderson.
Drills are available in steps 0,05mm below 1 mm either trough the internet or at a well assorted hardware store / machine shop.
This is how I played to get a correct main jet for my Tx4.
I allso found the cuffing when accelerating is depending on the idle jet setting (the external one).


For my Henderson deluxe 1928 I need a spare compensating jet #20, #21 or #22 in order to try curing "hesitation" before the main jet takes over. Originals or replicas - whatever is available.
Carl Henrik Stormer - Oslo, Norway