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<DIV><FONT face=Arial size=2>Hi,</FONT></DIV>
<DIV><FONT face=Arial size=2>I've just installed a brand new YS 91AC in a
Midwest Little Cap and started facing some problems. The engine was properly
broke in and really performed well in the test stand. As it was installed in the
model for flight (the fuel tank was tested before and after this experience) I
noticed that the mid range was "very rich" as the engine would take a lot of
time to reach full speed. I turned in the low speed needle valve but didn't feel
any performance increase, so I decided to turn in the pump screw in. I turned
the pump screw in almost two turns, as the engine showed an imediate response
from low speed to high speed. Anyway, the low speed still needed some fine
tuning but again I didn't feel any difference turning the low speed neddle valve
in or out, unless it was fully closed. Afterwards, I decided the engine was
running well for a test flight. I set the high speed needle valve to a slight
rich setting and took off. The engine acelerated weel on the take off, but after
a few turns on the sky and a cuban eigth with reduced throtle on the dives the
engine wouldn't accelerate imediately and sounded lean. In these ocasions I
backed the throtle and acelerated again with no problems, but now the engine
took more time to reach full speed and sounded richer than the set up made on
the ground. My experience with YS engines refers to a 120 AC that ran
beautifully rigth out of the box, with adjustments made only on the high speed
needle valve as these engine doesn't have a low speed needle valve. I'm using an
OS F glow plug and Wildcat fuel with 10% nitro/ 18% oil. If anyone can help me
with commentes, specially for the slow speed neddle valve that doesn't seems to
affect the way the engine works, or even a personal setting for the
engine I'll be more than glad. I almost forgot to mention that I recently
installed the same engine in a GP U Can Do 3D with another fuel tank, fuel lines
and YS Check Valve. The problem persists.</FONT></DIV>
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<DIV><FONT face=Arial size=2>Thanks in advance,</FONT></DIV>
<DIV><FONT face=Arial size=2>Fausto - Brazil</FONT></DIV></BODY></HTML>