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<DIV><FONT face=Arial size=2>Yes, sometimes the engine will ingest a bit of
debris and score the aluminum back plate causing a slight decrease in power and
a wetter than normal intake area. A piston/ring/sleeve fit nearing the end
of it's life will also cause an rpm drop and spitting but is usually accompanied
with richness at midrange and a difficult to adjust needle. Does the engine
still have the original "spool" piston ?? If so, in the future if not now,
replace it with the 0600 "bucket" piston from the standard YS120.
Durability will increase tenfold. There are 2 locking set screws on the
pin for the back plate rotary valve as well as the screw visible on the outside.
I have found the aluminum back plate not to be flat in most cases, I surface it
with 400 then 600 grit paper wet on a piece of glass and shoot for .002"
clearance between the disc ( rotary ) valve and back plate on reassembly.
Another problem area on the AC is the air chamber "O" rings, they tend to
wear from the weight of the airbox rocking side to side in a soft
mount. No matter how tight the screws are on the little strap from the valve
cover to the air box, the airbox can and does move a bit on the 4 "O"
rings.</FONT></DIV>
<DIV><FONT face=Arial size=2>Check the gasket for the air box also, most times
the mating surfaces of the 2 half's of the air box are not true and the
gasket will not seal correctly. No 2 tachs are exactly the same and rpm figures
are only meaningful if done with the same tach during the same atmospheric
conditions. If you are used to seeing 8300 with your tach and it wasn't a very
hot and humid day, it wouldn't hurt to take a look at the engine before
your next flying session. </FONT></DIV>
<DIV><FONT face=Arial size=2>Ed.M.</FONT></DIV>
<DIV><B>From:</B> <A title=johnferrell@earthlink.net
href="mailto:johnferrell@earthlink.net">John Ferrell</A> </DIV>
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<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 02, 2003 9:19
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Expected rpm on 120ac</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Spitting excess fuel is sometimes excessive
rotary valve clearance. Don't forget the locking setscrew if you go
there!</FONT></DIV>
<DIV><FONT face=Arial size=2>In my experience, AC's don't always look
impressive on the ground runup.</FONT></DIV>
<DIV> </DIV>
<DIV>John Ferrell <BR>6241 Phillippi Rd<BR>Julian NC 27283<BR>Phone:
(336)685-9606 <BR><A
href="mailto:johnferrell@earthlink.net">johnferrell@earthlink.net</A><BR>Dixie
Competition Products<BR>NSRCA 479 AMA 4190 W8CCW<BR>"My Competition is
Not My Enemy"<BR></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=drykert@rochester.rr.com href="mailto:drykert@rochester.rr.com">Del
Rykert</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 02, 2003 10:35
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Expected rpm on 120ac</DIV>
<DIV><BR></DIV>
<DIV><STRONG><FONT face="MS Sans Serif" color=#0000ff>Would appreciate
opinions.</FONT></STRONG></DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif" color=#0000ff>I have a YS 120ac that
has been a strong runner in the past. Would turn a 15x12 apc 8300-8400 on
25% powermaster. It was rebuilt last season but never run till this season.
It was giving me fits at Hamburg contest and taching is only showing 7800 to
8000. Needle 1 1/4 out. Seems to spit more fuel out of air inlet than I used
to see. </FONT></STRONG></DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif" color=#0000ff>My question being am I
being unrealistic expecting it to continue to give me 8300-8400 on that prop
& fuel. Valves check at 002 piston TDC cold. Good seal in valves. Don't
feel any drag from bearings but I replaced bearings last time and was
surprised on ratty they were after dis-assembly. Might my bearings be the
culprit and next item to explore?</FONT></STRONG></DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif" color=#0000ff>TIA for all who
reply.</FONT></STRONG></DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif" color=#0000ff> If you choose
to reply off list... <A
href="mailto:drykert@rochester.rr.com">drykert@rochester.rr.com</A>
</FONT></STRONG></DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff> Del K.
Rykert<BR> AMA - 8928 <BR>
NSRCA - 473<BR> Kb2joi -
General </FONT></STRONG></DIV>
<DIV> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face="MS Sans Serif"
color=#0000ff></FONT></STRONG> </DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>