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<DIV><FONT size=2>That's usually a detonation thing...meaning running it lean or
out of fuel....That's the normal cause for such a problem.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Also if the engines get really high time the con rod will get
an elongated or sloppy hole. Usually the problem happens on the crank side
first but it can happen up in the wrist pin also. I would just check the
wrist pin to make sure its still a cylinder shape and not "bowed" in the
middle or worn down. And then check the fit of the wrist pin in the piston, also
the fit of the wrist pin in the new connecting rod.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Check for play in the crank end of the connecting rod
also.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>If all is tight meaning no slop then you should be good to
go... Pay attention on the connecting rod. They are made to work one way. You
can tell by looking at the hole....one side will have a slight chamfer and the
other side will be more squared off. The chamfer side goes facing the
crankshaft....Some of the newer engines have a dimple mark on them and the
dimple faces toward the rear of the case. Just look at the bottom of the con
rod, right where the crank pin runs...you will see the difference between sides.
The one with the chamfer rides up against the rear or the
crank.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Then make sure the crank pin fits properly into the rear disc
valve assembly there is a notch in there that it rides in. If its not properly
aligned it will not run.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>happy flying.</FONT></DIV>
<DIV><FONT size=2>Troy Newman</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=paul.horan@sbcglobal.net href="mailto:paul.horan@sbcglobal.net">Paul
Horan</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, January 12, 2008 5:30
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] YS 120
NC/SC prop recommendation</DIV>
<DIV><BR></DIV>
<DIV>Troy,</DIV>
<DIV> As my last step before re-assembling the 120 SC I checked all the
parts carefully, good thing too. The con rod is cracked where the wrist
pin goes thru the bushing. Obviously I need to replace the conn
rod. Any cavats ? The piston and wrist pin look good.</DIV>
<DIV>Thanks,</DIV>
<DIV>Paul<BR><BR><B><I>"Troy A. Newman" <<A
href="mailto:troy_newman@msn.com">troy_newman@msn.com</A>></I></B>
wrote:</DIV>
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<DIV><FONT size=2>For the 120NC just prop it down a size...maybe 2 sizes.
The 15-10 might work well. You might also look at a 15-9 or 15-8 will likely
be bit too light. Personally the props used are usually about the same. The
120's didn't have that huge of a power difference. The 120SC was the
strongest, and the 120SF-120NC-120FZ were all about the same..the 120AC was
in between the two levels. The problem with the AC was the air box and the
extra weight.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>What you want to do is run the engine at about
8500-8800rpm as a target rpm. What ever fuel/prop combo gives you this rpm
will work the best on the engine. Regardless of the engine turn the rpm
range an it will be happy and make good power.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>For reference there were some 14in props that were really
good too. The 14-12...and the 120AC liked the 14.5-14N. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>My guess is try the 15-10 and see how it performs on the
top end rpm. If you are below say 8400 then either up your nitro or lighten
the load.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>As for replacing the sleeve. If there are deep scratches,
or when the crosshatch pattern is completely gone. If its just smoothed out
at TDC this is typical and happens pretty quickly. but when it starts to
wear down about 1/3 to 1/2 way down the pistons travel then its time to
start looking for a new sleeve. Any of the 120 sleeves will work. Same way
for the piston....check it to see if its round in all directions. Look for
play on the wrist pin. Inspect the ring groove. The best piston to run is
the original 120FS as its the most robust. For maximum power and performance
the magnesium pistons are awesome but they are more fragile. The dished
pistons again better power but more fragile. Don't run them lean and they
will be good to go.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>As for the fuel that was left in them....not sure what
fuel you are using but I have not had this problem with the Cool Power. Some
other fuels that are highly touted by some...well I had problems there.
Another note if the engine is going to sit for a long time. I place it in a
plastic bag and put it back in the box. It resides in the house. Temperature
changes are minimal...you don't want to leave it where the temps will go
through extremes. This will invite condensation and moisture. That is where
the rust comes from.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Troy Newman</FONT></DIV>
<DIV><FONT size=2>Team YS</FONT> </DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=paul.horan@sbcglobal.net
href="mailto:paul.horan@sbcglobal.net">Paul Horan</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, December 30, 2007 9:31
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] YS
120 NC/SC prop recommendation</DIV>
<DIV><BR></DIV>
<DIV>Troy,</DIV>
<DIV> Thanks for the info. </DIV>
<DIV> I have one 120 NC and one 120 SC, the NC will go on an
Aires and the SC will be a backup. Both required a rebuild, looks
like they were left with some fuel in them and left that way for
years. All the bearings needed replacement, including the camshaft
bearings. The SC has a piston with a concave top, (dished
?). Of the two engines the SC is in the best shape, the crosshatch
tooling marks are visable in the cylinder. The NC compression
could be better. Any suggestions for running the NC ? How do I
know when I need to replace the cylinder sleeve. </DIV>
<DIV>Thanks again for the info, in this case more is better.</DIV>
<DIV>Paul</DIV>
<DIV><BR><B><I>"Troy A. Newman" <troy_newman@msn.com></I></B>
wrote:</DIV>
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<DIV><FONT size=2>15-10 is an excellent prop on the 120SC, if its a
strong one you can with the 15-11</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Of special note the 120SC likes Nitro. It is a fairly
high compression engine and can be a little finicky. It was the
strongest of the 120's In fact I had one that gave the 140FZ a run for
the money.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Being this soupped up highly tuned 120...the extra
nitro broadens the mixture settings. The other thing it does is higher
nitro require richer settings to get the mixture correct and as a result
they will run a bit cooler and better. More fuel flow means more oil
flow and better cooling also.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I strongly recommend the Cool Power 30% heli
fuel.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>By the way, on the 120SC because its more a higher
compression soupped up version, don't run it out of fuel. If you are
flying and too long and the engine runs dry it can backfire and can
cause damage. Its never a good idea to run any of the pattern engines 2
or 4 stroke out of fuel, however the 120SC, 120AC, and the 140DZ tend to
be a little brutal when this happens. Try to run the 120SC at the higher
end of rpms. I would say the goal rpm for that engine would try to be up
at 8600-8800 maybe as high as 9000. On the 15" props it will make noise
with ease in most cases(read exhaust systems)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>The 120SC is an awesome engine. Like I said it was the
king the of the 120's. There were some folks that had issues with them,
but my experience was always good with the SC. There were some piston of
the month changes to the 120SC. Namely they had a dished piston, and
some magnesium pistons. The goals behind these were to get more power
out of the 120 case. Back then the FAI rules had not changed to allow
larger than 120 displacement. So YS was trying to lighten the piston,
and get the engine making max power from the little box. At the time
there were a few models that were getting bigger than the 2 meter box as
the 2m box didn't exist. No size limit just the engine limit and the
weight limit existed at the time. On the piston front just stick any ole
120 piston in it....the 120SC piston could be a little fragile if run
lean (meaning running it out of fuel). The original 120SF piston was
bullet proof and works in the 120SC. The dished and designer pistons are
really able to change the behavior of the engine. I have played with
this "super" or the "hyper" pistons on the current 160DZ and
170DZ engines. Its cool how changing the piston by putting a dished top
and closing off the bottom of the piston can change the way the engine
reacts to certain prop loads, or it will change the noise. Some of the
things they can do make more power and some of the pistons make it run
super smooth and quiet. Yamada doesn't do the testing in production like
they once did with the pistons. I have been fortunate to try some of the
super cool, "hyper" pistons they have played with on the DZ's. I wish I
had the knowledge back then that I have now. Some of the smallest
changes in a piston can really totally change the way an engine
performs. Its kinda neat. I remember the need was for more power more
power back then and now I know which piston designs would have done it
better. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Any of the current exhaust systems will work very well
on the engine. Even the short hatori 821 pipes and the NMP header will
work excellent on that engine.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I have a couple of 120AC's that we carved up the
heads to get more power...I wish I still had the 120SC as it would
be a really good engine for my war bird project I'm planning. I actually
need a pair of the 120SC's for it. Right now the 120AC's are a little
heavier than I would like and have been considering putting a pair of
140 Sports in the model.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I know this was likely way way more information
than you needed to know. But its a good engine and you'll love
it.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Troy Newman</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=flyintexan@comcast.net
href="mailto:flyintexan@comcast.net">flyintexan</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, December 29, 2007
8:53 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
YS 120 NC/SC prop recommendation</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Should be able to run a 16x8 on
30%...</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=paul.horan@sbcglobal.net
href="mailto:paul.horan@sbcglobal.net">Paul Horan</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing
List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, December 29,
2007 6:09 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [NSRCA-discussion] YS
120 NC/SC prop recommendation</DIV>
<DIV><BR></DIV>
<DIV> Any suggestions for a YS 120 prop ? It will be on
a Aires ?</DIV>
<DIV>Thanks,</DIV>
<DIV>Paul<BR></DIV>
<DIV>
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