ORIGINAL: JDW
In my earlier post today I should have added that :-
1/ The idle needle on these engines is very very sensitve. It MUST be set correctly and 10 degees rotation can have a dramatic effect. By comparison OS (and some other) engines are quite tolerant of slightly rich idle settings and generally their idle srews are not unduly sensitive - within 1/2 turn is OK.
Within 1/2 turn is ok on other carbs????
2/ The idle needle must be AS LEAN AS POSSIBLE. Remember that the idle needle WILL effect the position of the main needle for full throttle performance.
Closing the idle needle even a few degrees should make it too lean -i.e. it should just die when the throttle is opened.
If you are doing this your engine will quit running quite often in flight
when you throttle back to idle after running full blast and the engine
is hot. Adjusting the low speed lean is inviting deadsticks.
The really confusing and undesirabe characteristic of the design of these carbs is that an incorrectly set IDLE MIXTURE will effect mid range and full throttle performance dramatically and yet the engine may well idle really nicely!!!
Really? An incorrectly set idle will idle nicely?
Put a front needle carb on the engine and it will act differently. The problem
with these engines is quitting in flight even when the seem to be running ok
on the ground. When an engine quits in flight it is from leanness and overheating.
MB