[NSRCA-discussion] OS-120AX questions/thoughts... yes again

[Ihncheol Park]

Jason,

Sounds like not enough muffler pressure for tank.  Pump, regulator, header
tank, or a Macs one piece muffler (not exactly sure if the pressure is
higher on Macs muffler, but it usually increase output a little) may help.

OS used to sell a fuel nipple that has longer threaded side. One that some
of us used on 160 back plate for crank case prssure?  I once moved the
nipple from the muffler body to exhaust port side to increase the pressure.
If you can find a longer threaded fuel nipple, grind about 1/2 of the
threaded side in angle.  Then, install it facing the exhaust.  It helps one
a couple of old engines.

Are you using Control Line fuel?

Ihncheol

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of J Shu
Sent: Sunday, September 20, 2009 3:43 PM
To: General pattern discussion
Subject: [NSRCA-discussion] OS-120AX questions/thoughts... yes again

Hi All,

I've posted in RCU about some issues I'm having with my OS-120AX and was
wondering what you might think?

Here's the the link: http://www.rcuniverse.com/forum/m_9110170/tm.htm

And what it says:

I'm hoping this thread will help answer some questions about the OS-120AX
that I am having.

I've got it in an 8lb 2oz, 110 sized pattern plane, stock muffler, 420cc
tank (14oz), OS-F plug, 3-line system (Vent, carb clunk 
line, fill clunk line), 15x10 APC and for break-in, PowerMaster 10% with 29%
Caster... will switch to 15% with 16-18% Synthetic 
after this gallon.

The tank is fairly close to inline with the carb, maybe 1/2" higher. On
neg/inverted pushes the motor seems to starve until I close 
the throttle a little. On pos/upright pulls it seems ok, maybe a slight
richening. There is a nice smoke trail as after my first 
flight I wasn't rich enough and the flight ended a bit early. I'm sure it
will run a bit easier after it's broken in, but has anyone 
tried a foam clunk like the YS's use?

Any other tips? It has enough power with this set-up to go through the F-09
sequence, but about half way through it starts this 
'cutting out' deal. It's just annoying to have to power back as you're
climbing to keep it running.

Also, what differences has anyone noticed flying the 15x10 to 16x8 in
testing.

Regards,
Jason
www.shulmanaviation.com
www.composite-arf.com

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion