I have an old YS 120 vFZ that I bought new in 1995.
It has run great for many years.
It recently blew the con rod right below the wrist pin.
Richard overhauled the engine for me and I have run half gallon of fuel through it set very rich for break in.
I have a 16x8 prop on it, runs at 9100 peak and richened to 8800 rpm for flying.
(needle valve 1 1/2 to 1 5/8 open)
Using Wildcat 15% with 18% oil and several ounces of castor added to bring it up to 20%.
Has worked good for 15 yrs now.
The problem is the engine goes richer as the flight progresses.
When first started and warmed up a little, if I open full throttle, its very strong, 8800rpm.
iIf I bring it down to idle(2000RPM) it will idle fine, but when I throttle up its very rich.
Lots of smoke and maybe 7500 rpm.
I have set it according to Rick Matties instructions.
This was the first engine with an idle adjustment, its at 3 or more turns open, have tried many different settings.
It drops right down to 2000rpm and is steady at 3 turns open.

Thanks for any help,

Pete Stapleton