More Bings

[John Ehrhart]

Can someone explain why my 1/27 on the Sachs 6B takes a 40 idle jet while my Jackpiner takes a 30 to be happy? Seems illogical, but I realize they are carbs!

[firstturn]

John,
  Are you just trying to understand how carburetors work or are you not understanding why a smaller caburetor, and smaller bore engine for that matter, takes a smaller pilot jet?  I can give you some sites to answer number one and as far as the 27mm taking a larger size pilot it could be one of many reasons.  Carbs of the same make and size can vary on the size of jets just due to manufacturing differences.  Also on carbs that have wear on them the jetting can change.  You didn't mention what altitude you are jetting which can also make a difference on jetting of smaller bore carbs verses larger bore carbs.  Also sometimes the design of the slide can change the need for a smaller or larger pilot(I don't think this is the situation in this case).  Ansd as you said illogical is a key term when dealing with or trying to compare two different carbs.

Ron Carbaugh

[Merlin]

...........the same bore carb on a small engine vs a larger one will require larger jets because the negative pressure signal is reduced due to engine size,meaning the smaller engine moves less air(less air signal to move fuel) needing a larger fuel metering orfice to allow the flow for proper air/fuel ratio..................

[John Ehrhart]

Ah! I knew you guys were good.
Thanks for the explanation.