I have had others also ask for help with these beauties. Have gotten several PM's asking for help.

We have five running here, running well, super powerful, very reliable. But
they don't come out of the box that way.

Try the following:

Fuel: For best results use 5% nitro fuel, at the most 10%. The engine has
high compression and 10 - 15% fuel can cause pre-ignition - which is
probably what you hear as a crackling noise in the air. You can use a shim
to lower compression if you really have to use 15% fuel, but the 5% fuel is
cheaper and it performs very well with it. A cold glowplug may help to
prevent pre-ignition in flight at higher throttle settings with 15% nitro.
Most of us here use 5% fuel (with 18% oil - of which 1/3 is castor oil 2/3
is synthetic oil ) with an OS 8 glowplug or a Hanger 9 Superplug.

This problem: "decides to cut out on transition from low rpm to high rpm.
This happens on takeoff runs or in the air" is most likely due to a too rich
low speed needle valve setting. At idle before take-off the engine loads up
with unburned fuel and then douses the glowplug when full throttle is
applied for take-off. This also causes a too rich midrange with lousy
transition from idle to full throttle. Although each engine differs a bit,
most of the engines here run best with the low speed needle less than one
full turn out from the fully closed position. A good start point for the low
speed needle ( also known as the idle screw ) is 0.75 to 1 turn out from
fully closed (turned in ). Do this adjustment with the throttle fully
closed. To adjust the low speed needle, the high speed needle must bet set
first. First set your high speed needle for max rpm, then back it out a few
clicks ( approx 300 to 400 rpm ) to avoid running too lean at full throttle.
When it is adjusted correctly, then let the engine settle into a slow idle
for about 40 to 60 seconds. Now pinch the fuel line. 1) If the engine quits
almost right away, it is too lean, turn the low speed needle out
(anti-clockwise ) approx 1/8th of a turn and repeat the test. 2) If the
engine speeds up significantly when the line is pinched, it is too rich,
turn the low speed needle in ( clockwise ) approx 1/8th of a turn, and
repeat the test. The correct setting is where the engine speeds up for only
a few seconds and then quits. When adjusted correctly it should idle
reliably, and will have very good transition to full throttle. Once the low
speed needle is set, just double check the high speed needle again. It
should be close to perfect.

Prop choices : fun flyers - try 11 x 5 or 11x6. For 3D try an APC 12.25 x
3.75. For faster sport flying try 10 x7 or 10 x 8. For a racer (such as
Great Planes Viper) try an APC 9x10 - awesome ! !

This engine is a honey. I find that they seem to settle down after approx 10
to 15 tanks of fuel.

Also :check for fuel line leaks, fuel tank position problems ( tank too high
? ? usually in inverted engines ), leaking remote needle valve (slip some
fuel tubing over it if it leaks.), and seal the muffler segments with
"Loctite sleeve retainer".

Hope this helps.