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<DIV><FONT face=Arial size=2>John</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It's likely that the DZ isn't any more susceptible
to air in the fuel supply than any other engine, just that the "standard" YS
pressure system is very good at preventing those sort of problems. I've run 3
DZ's in a couple of different airplanes with a variety of fuel systems.
Generally, they all work well and include a bladder, an open vent / foam clunk,
check valved vent / foam clunk, pipe pressure / regular clunk, combining for
around 100 gal. of fuel or so. I've settled on an open vent / foam clunk system
with the vent routed behind the tank, then forward (1/8" aluminum tubing) to
exit.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>All the various systems work well, however any
configuration that doesn't relieve expansive pressure (say, from sitting in
the sun), as well as bladder systems or a high tank, will flood the engine
unless some form of positive fuel shut-off is incorporated.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I've seen a couple of systems where the tank was
solidly mounted for use with an L that would result in a lean stoppage a couple
of minutes into the flight with a DZ. Our old friend - fuel foaming. These
systems will generally run OK on the ground as vibration is damped by holding
it. Go back to basics and isolate the tank from vibration, the foam clunk
may reduce this problem but not fix it.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If a high time DZ begins to sag on uplines as the
tank nears empty it's likely that there is wear between the upper pushrod and
the pump housing. It's simply easier to draw air from the high pressure area of
the rocker cover plenum than fuel from the tank a foot or so below the pump.
These engines will also tend to load up during sustained idle as fuel is
leaking, via the same route, into the (now) low pressure area of the rocker
plenum. Replacing the upper intake pushrod and pump housing fixes this. This is
not likely a problem with an engine not having used 50 gal. of
fuel.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Earl</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=jlees@mwdh2o.com href="mailto:jlees@mwdh2o.com">Lees,John W</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> Thursday, May 13, 2004 11:33
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: YS 140 DZ going lean in -ve
g maneuvers</DIV>
<DIV><BR></DIV>
<DIV><SPAN class=004212816-13052004><FONT face=Arial color=#0000ff
size=2> I thought DZ's were crap, had several different tanks, clunk's,
ect. Not until I went to a Bladder tank{no air in media} did the engine run
flawless. Since then it has never even hick-upped. </FONT></SPAN></DIV>
<DIV><SPAN class=004212816-13052004><FONT face=Arial color=#0000ff size=2>It
is of my opinion that the DZ will not tolerate any air in the fuel delivery
system. --john</FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> PENNISI Peter
[mailto:Peter.Pennisi@publicworks.qld.gov.au]<BR><B>Sent:</B> Wednesday, May
12, 2004 5:29 PM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B> YS
140 DZ going lean in -ve g manoeuvres<BR><BR></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=308181500-13052004>Hi
all,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=308181500-13052004>My
DZ has only returned from holidays in Japan were it was repaired by YS from
another cam failure.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>The engine is running absolutely superb except when
you pull high negative g manoeuvres like the reverse humpty bump it gets a
little lean for a few seconds put it does come good.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=308181500-13052004>I
have re-plumbed the model put the problem is still there.
</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Running</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>APC 16 x 12</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=308181500-13052004>OS
F plug</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Tetra 20 oz tank with OS sintered(Spelling) bubble
less pickup.(Yes the expensive one)</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Hatori exhaust (698 pipe)</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Coolpower 30% heli blend</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Model is ZN-LINE Alliance.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Any suggestions</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004>Peter</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=308181500-13052004></SPAN></FONT> </DIV><!--[object_id=#publicworks.qld.gov.au#]-->
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