Model Forum / Radio Controlled / Helicopters / July 2008

I was always lead to believe two turns out will always start the engine and
back it of if it start to over fuel i.e. smokes a lot and starts to bog down
under load. there is no a exact setting every engine/ carb is slightly
different, plus the weather conditions ambient temp etc all contribute to
how much fuel is needed.

Rob

Needle setting is sensitive to exhaust pressure (if used) and the
height of the tank in relation to the carburetor.

If your tank height is where it belongs and you are still rich the
muffler may be clogged. Most needle assemblies work best at about
1-1/2 turns open. All OS engines I have experienced will run rich at 2
turns open but will be right closer to the 1-1/2 turn settings.

All Pitts mufflers I have tried have poor exhaust pressure.

Note that I am a Heli wannabe but a fair amount of fixed wing
experience!

John Ferrell W8CCW

Sounds like you're on the right track.  With a new glo plug and once you get
the mixtures where the engine is happy, you should be Ok for a while.  One
thing I've run into many times over the years is that I'll have a good
running heli for weeks or months at a time and then it'll start going a
little sour.  What did I do?  I started futzing with the mixture of course.
After fighting that for a while it finally occurs to me to try changing the
glo plug.  Once that's done, then I spend the next two tanks of fuel putting
the mixture back where it was to begin with because the problem was really
the glo plug.

I'm not saying that was your issue all this time.  My point is, once you get
it happy, and it sounds like you're really close, if you have to change the
mixture more than a couple of clicks one way or the other because of a
weather change or something then it's probably the glo plug.  Even if the
plug is relatively new, when it doubt, change that sucker.  I've gotten bad
ones right out of the box so you never know.

Good luck with it RoRo, and fly Safe!
Steve R.