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<p class=MsoNormal><span class=EmailStyle24><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'>What size
prop are you running and fuel mix? I felt that more RPM’s or running leaner
(more heat) would produce more exhaust gas volume thus more back pressure and
probably be better. I am running a 16-10 APC on 10 or 15% nitro, cool enough
that the discharged oil is the same color as the fuel. I purchased the first
engine 8-03 and the second 4-05. The carburetors were different (see attached
photo). The one on the left is from the first engine. The idle mixture (tapered
needle) didn’t completely withdraw from the fuel delivery tube and the barrel
had a small hole through the side like the parts drawing on page 42 of the
manual. The second one didn’t have this hole. I felt that when the barrel
pulled out at full throttle without fully withdrawing the idle mixture needle
presented a second fuel restriction, a condition I have seen in the past. When
inquiring as to which carb was correct (revision or Mfg error?) from the
service center I got the expected response. They either didn’t know or were not
about to explain the difference to me after all I am a small fish on their pond
and have never read anything about a revision. </span></font></span><span
class=EmailStyle24><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial;color:navy;mso-color-alt:
windowtext'><o:p></o:p></span></font></span></p>
<p class=MsoNormal><span class=EmailStyle24><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'>Which carb
do you have?</span></font></span><span class=EmailStyle24><font size=2
color=navy face=Arial><span style='font-size:10.0pt;mso-bidi-font-size:12.0pt;
font-family:Arial;color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></span></p>
<p class=MsoNormal><span class=EmailStyle24><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'>Jim Hiller<o:p></o:p></span></font></span></p>
<p class=MsoNormal><span class=EmailStyle23><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></font></span></p>
<p class=MsoNormal><span class=EmailStyle23><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></font></span></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:black'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org]<b><span style='font-weight:
bold'>On Behalf Of </span></b>Jay Marshall<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, October 22, 2007
3:51 AM<br>
<b><span style='font-weight:bold'>To:</span></b> 'NSRCA Mailing List'<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion] OS
120AX header?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>I believe that the stock
silencer for the 120AX has quite a bit of back pressure. In my Venus I
moved the fuel tank to the most reward possible position and tried it w/o a
pump. No difference in performance from the forward position even on long verticals.</span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p style='margin-left:.5in'><b><i><font size=4 color=navy face="Brush Script MT"><span
style='font-size:13.5pt;font-family:"Brush Script MT";color:navy;font-weight:
bold;font-style:italic'>Jay Marshall</span></font></i></b><font color=navy><span
style='color:navy'> </span></font><font color=black><span style='color:black;
mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:black'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Bob Richards<br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, October 06, 2007
9:22 PM<br>
<b><span style='font-weight:bold'>To:</span></b> NSRCA Mailing List<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion] OS
120AX header?</span></font><font color=black><span style='color:black;
mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>Jim,</span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>I have not
run my 120AX enough to conclude anything yet, but the little bit that I have
run it left me thinking there was not enough muffler pressure either. I tried
with/without the internal baffle, but I think the best combo would be to leave
the internal baffle out and try restricting the tailpipe as you say.</span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>There are a
couple of guys in our club that have the 120AX running the Jerry Smith mousse
can mufflers and get MUCH better performance, and more reliable running as well
since there is considerably more muffler pressure. They also fly several Outlaw
delta planes with .32 size engines and do incredible manuevers, using the
same type muffler setup. The only way they can pull the Gs they do and still run
is because of the much higher backpressure.</span></font><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>With a large
volume muffler (the larger the better) the more pressure you can run in the
muffler and the engine still run fine. In fact, you will burn less fuel as well
since less excess fuel/air mixture blown out of the exhaust during the exhaust
scavenging.</span></font><font color=black><span style='color:black;mso-color-alt:
windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>I did a lot
of muffler/prop experimenting (sport planes) many years ago. :-) I learned a
LOT.</span></font><font color=black><span style='color:black;mso-color-alt:
windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>Bob R.</span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'> </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'><br>
<b><i><span style='font-weight:bold;font-style:italic'>J N Hiller
<jnhiller@earthlink.net></span></i></b> wrote:</span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<div style='border:none;border-left:solid #1010FF 1.5pt;padding:0in 0in 0in 4.0pt'>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'>16 x 10 should be no problem. I have run one all season
with stock muffler. I didn’t like how many RPM’s the 16 x 8 turned in
horizontal flight.</span></font></span><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'>This may be a little off subject but may be of
interest to other 120AX users.</span></font></span><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'>I fought a rich midrange (poor transition) from day
one in order to keep from running too lean on a long vertical pull, which
seamed to get worse in cool air. I have two motors that have different
carburetors and focused on this as a problem even though both acted similar
eventually concluding that there wasn’t enough muffler pressure. I have never
gotten along well with pumps so I tried restricting the muffler outlet using a
short exhaust tube (3/8” ID) with a brass tube insert. I tried a couple
different sizes settling on 13/32 OD, which is pinched on the end from cutting
with a tubing cutter (.350” ID). Flaring the other end keeps it in the exhaust
tube without clamps. I also tried an OS-“F” plug which I thing may be better
than the #8. It will be 9 months before I can run it in hot weather but I was
able to run leaner without starving in the verticals and the transition is
immediate.</span></font></span><font color=black><span style='color:black;
mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Jim Hiller</span></font></span><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Spokane</span></font></span><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:
0in;margin-left:75.75pt;margin-bottom:.0001pt;border:none;mso-border-left-alt:
solid #1010FF 1.5pt;padding:0in;mso-padding-alt:0in 0in 0in 4.0pt'><span
class=emailstyle20><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial'> </span></font></span><font color=black><span
style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
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color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
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