YS .91 idle setting

[Troy Newman]

on YS motors all except the DZ the magic number on idle RPM's is 2000....not
2200 not 1900....2000 even....The reason for this is at 2000 rpm the motors
are no longer being force fed fuel...rather they are sucking it.....like a
normal motor....To set the idle you need a tach...trim the rpms to 2000 even
then watch the tach...if it surges slightly up then down and dies off its
lean...if it sets at 2000 and the just dies off 19-18-17 dead...its rich....

On the FZ style motors (140 FZ, 63FZ and so on....) The 91AC and the 120SC
the throttle barrel has a Idle adjustment air bleed screw...On the screw on
the throttle barrel in is rich and out is lean....In some case you can take
the screw almost out and its not lean enough. This is the case on early
motors with this function.....There are 2 fixes...Take the throttle barrel
out and remove the adjustment screw completely...then drill the hole in the
butterfly larger...Re-install the screw and you now have more adjustment
available as the bigger the hole the more lean you can make it...This is a
rare need...But I have had it happen....The regulator adjustment is made at
about 3000-4000 rpms.....Set like 3500 even...The watch the tach if it
climbs then falls off the regulator is lean...dial it out...If the motor
just slows down then its rich....

Now at the idle setting if its too rich..before you re-drill the air bleed
hole chances are the regulator is building too much pressure...meaning its
rich anyway....So try to setup the midrange first.


OK these are the adjustments.....order of operation is......High end needle
first...then idle...every change to the low end idle means you need to clear
the motor out and then reset tot he 2000 rpm and see what happens
again....Then once the idle is set re-do the high speed needle....Then
re-check the low end...Once they are good then go to the regulator and set
the mid range....The go through the process again...Highend-low end-mid
range.....they will all interact a little....

another thing with the mid range...If the motor is running fine at first but
richens up after just a couple minutes of flying then the regulator is
probably a little rich...Dial it out...What is happening is as pressure
builds too much pressure gets built up and the motor is being force fed
fuel....Leaner on the regulator means less pressure...hence less
fuel....This is not a fuel pump...It pumps air! and meters the pressure in
the tank.

#2 goal is to not get the motors too hot on the ground...If you are running
more than about 2-3mins on the ground jacking with the setting its too long
and the motor is hot...Shut it down let it cool off then start again...Once
they are hot you will never get them set right....so they need to be watched
when running on the ground...If its good enough to fly..fly it and make a
minor adjustment next flight. The worst thing you can do to a motor is
ground run it..jacking with it...It gets hot...In the air the air flowing
past cools thing down....On the ground the prop doesn't move enough air over
the and around the motor...

As the motors break in from new the settings with stabilize....when they are
new...a richer setting is achieved because the motors parts are tighter and
make more heat...as the motor breaks in the setting will be too rich to run
and needs leaning...Usually this is high end and sometimes the low speed
idle...but rarely the regulator screw....

Starting points......High speed- 2 turns open, Low speed 1.5 turns
open...Regulator screw flush with the case...maybe a little inside the
case...You will always want the idle a little rich...So transition takes
just a few moments....and instant screamin' eagle will make for a hot
running motor as the instant throttle up will cause the motor to go slightly
lean then richen up...You can usually see this in the smoke trail the motor
has...As the motor will smoke slightly then go away and then smoke
more....This is a little lean in the middle...Smoke at the very bottom-mid
range and top end is great...Of course the volume will vary but the color of
the trail should be pretty constant....The High viscosity oils like the Cool
Power Heli Pro 20% or 30% work great in the DZ and also in the std pressure
systems of the YS....these fuels will smoke a little more.....and I have
just started setting my motors based on my tach for idle and my ear and the
smoke trail...I can tell by flight times and by looking at the trail if the
motor is too rich or lean.....

Ok hope this helps you out....
good Luck

Troy Newman
----- Original Message -----
From: "Craig Miller" <cmiller51 at hotmail.com>
To: <discussion at nsrca.org>
Sent: Tuesday, April 08, 2003 5:48 AM
Subject: Re: YS .91 idle setting


> I have an AC that I've been flying with for the last two summers, and I
> don't think I have the idle down to 2000 RPM, maybe at about 2400. It
might
> be that you have the idle too low (especially for a new engine). All you
> need is an idle slow enough to land, and of course so the ship doesn't
start
> rolling before announcing your take off!
>
>
>
> Craig Miller
> Remsen, Iowa
> AMA 66900
> NSRCA 2255
> http://user.midlands.net/cmiller
>
>
>
>
>
> >From: "Keith Hoard" <khoard at midsouth.rr.com>
> >Reply-To: discussion at nsrca.org
> >To: <discussion at nsrca.org>
> >Subject: Re: YS .91 idle setting
> >Date: Mon, 7 Apr 2003 17:12:43 -0500
> >
> >Yup, got that. . . left is lean, right is rich. . . Just came in from
> >messing with the low speed needle and it is set good for the transition,
> >but it still won't idle for more than 20-30 seconds.  I run it full
> >throttle for about 10 seconds to pressurize the tank then drop it to
idle -
> >2000 to 2400 RPM.  The engine idles at this speed for about 20-30 seconds
> >then the RPM slowly decays until it quits, then fuel drips out of the
carb
> >(engine inverted).  I relight the glow plug, spin the engine and it
starts
> >right up again and repeats.
> >
> >
> >
> >Keith L. Hoard
> >Cordova, TN
> >klhoard at midsouth.rr.com
> >   ----- Original Message -----
> >   From: Terry Brox
> >   To: discussion at nsrca.org
> >   Sent: Monday, April 07, 2003 5:03 PM
> >   Subject: Re: YS .91 idle setting
> >
> >
> >   Low speed is an airbleed. Out is leaner, in is richer. Opposite from
the
> >high speed.
> >     ----- Original Message -----
> >     From: Keith Hoard
> >     To: NSRCA Mailing List
> >     Sent: Monday, April 07, 2003 4:51 PM
> >     Subject: Fw: YS .91 idle setting
> >
> >
> >
> >     From: Keith Hoard
> >     To: NSRCA Mailing List
> >     Sent: Monday, April 07, 2003 3:06 PM
> >     Subject: YS .91 idle setting
> >
> >
> >     Gentlemen,
> >
> >        I'm breaking in my YS .91FZ and seem to have gotten the top end
> >working fine, but the engine idles at 2000 RPM for about 10 seconds then
> >slowly dies.  I don't remember which way to turn the low speed needle,
and
> >the YS Performance page seems to have been hijacked.  Thanks!!
> >
> >
> >
> >
> >     Keith L. Hoard
> >     Cordova, TN
> >     klhoard at midsouth.rr.com
>
>
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