Model Forum / Radio Controlled / Land Models / March 2005

The usual starting point for the middle needle screw on any 3 needle carb is
get the screw head flush with the side of the carb body, they usually only
get moved about +- 0.5 turn from there as a fine adjustment to the pickup
response. If your mid-range needle is currently 1/8 turn open then you will
need to close the bottom needle about a turn or more to compensate for the
mid-range needle needing to be opened up.

From what you're describing either the idle gap is too small or the bottom
end needle is too far closed, start by re-setting the airgap (take the carb
off the engine to set it... it's far easier to see when you can see through
the carb) wind the top end needle out to flush with the top of the brass
tube it sits in (it'll be rich but run) and then do your blow test (use lung
pressure i.e blow through it through a bit of fuel tubing!) to set the
bottom end needle. That will give you needle settings that will get any
engine to run and you can adjust from there.

Here are the basic settings from www.rchobby.com  for the Wasp .28:

Default high speed Needle setting 4.5-5 turns from closed.
Default low speed needle 4-4.5 turns from closed.
Barrel stop screw (idle/tickover speed adjustment) 1/16th gap.
Normal engine operating 280 degrees F.
All settings are approximate

Chris