[NSRCA-discussion] First day out with OS 140RX (somewhat long)

[Mike Hester]

That's a good, honest comparison.

One note: I'm betting that your bottom end is set rich, and that's why 
you're idling at 2000, and why it flamed in a high G. Probably when you got 
back into the power, it drowned the plug. The OS likes a lean bottom end. 
Are you using an F plug? Turn the idle screw clockwise about 1/8 turn and 
your idle speed should actually increase. Then dial down your trim until you 
hit about 1800 or so. It will go lower, but until you get used to it, 1850 
is good.

-Mike

----- Original Message ----- 
From: "David Flynt" <dflynt at verizon.net>
To: <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, March 01, 2006 7:40 PM
Subject: [NSRCA-discussion] First day out with OS 140RX (somewhat long)


> Today was one of those beautiful California days, in between the rain, and 
> I
> have the week off, so I finally got my ZNline Supreme in the air for 
> several
> trim flights.  Also, I switched from the Webra 160 with M/C to the OS 
> 140RX.
> Below are my initial impression of OS, along with comparison to YS 140DZ:
>
> I was particularly careful while breaking in the OS.  I wanted to ensure 
> no
> problems, and the engine was ready for fly time.  I broke in on the bench
> with one gallon of fuel.  I saw 7800 rpm with a 16.5x12w prop mounted in 
> the
> plane today, fairly rich.  I'm hoping I have it set way too rich, and that
> it will gain more power as I get more fuel through it.  My setup is a Karl
> Mueller header at 9 3/8 inches from from exhaust flange to the entrance of
> the pipe, and an ES 2C140M80 muffler.  Cool Power 15%.  The Mueller header
> has a sharper rise over the OS or Hatori header, and I needed that to 
> clear
> my firewall.  Total length due to the sharper rise is near the same as the
> stock OS header.  What a nice header BTW.  It has the right thrust built 
> in
> so it is straight down the middle of the pipe tunnel.  It came with a 
> short
> extension so that there is stress relief on the header to prevent it from
> breaking.
>
> Big two strokes are new to me.  Before this engine, I was running a YS
> 140DZ, and before that, YS 120 - 140.  Here are my initial observations 
> and
> comparison between the 140DZ and 140RX:
>
> Ease of use:  Probably a toss up.  The OS is very user friendly, and is
> simple, and runs on sport fuel.  It is not as easy as the YS in that you
> need to tune header length and select optimal prop and muffler/pipe, 
> however
> for the OS you can stand on somebody else's shoulders, and that is what I
> did for the most part.  I don't know if I am done tuning it however.  Both
> engines are pretty much hands off once broken in and set (at least what I
> hear for the OS).  I flew 300 times with the DZ, and never touched the
> settings after break in.
>
> Ease of start:  Hands down, OS.  This engine starts with ease.  The DZ, 
> once
> you learn it, will start easy so long as you have a strong starter and
> strong glow source.  But it can lock up on you if you allow it to flood.
>
> Idle:  Definately the OS.  I had a good idle after one gallon, and I still
> have not touched the low end from factory setting.  The YS will idle ok 
> for
> a while once warmed up, but it won't idle forever.  It does not really
> matter so long as you do not let it idle for long periods.
>
> Reliability:  No way to know since I don't have time on the OS, but one
> strike against it today.  It flamed out at the bottom of the reverse
> avalanche.  I just made it back, heart pounding all the way.  This is
> probably an anomaly, and I only have 1 1/2 gallons through it (I should 
> not
> have been practicing the reverse av with such little time on the engine, 
> but
> oh well).  Idle speed was 2000 on the ground.  On the first flight 
> however,
> I overshot the runway twice, and I had to go around.  So, it stayed lit 
> when
> it counted.  The DZ never flamed out during flight.  I speculate that the 
> DZ
> is more reliable, but I am splitting hairs.
>
> Quietness in the air:  OS is quieter, like a whisper compared to the DZ. 
> DZ
> has a lower pitched noise.
>
> Vibration:  OS is much less vibration and very smooth at idle through full
> thottle.  There is an area about 1/4 throttle where it shakes a little, 
> but
> not bad compared to the DZ.  The 160DZ I hear is a lot smooother than the
> 140DZ, which would be nice.
>
> Torque:  Hands down, the DZ.  The DZ has a smooth, linear throttle curve 
> and
> usable torque at any throttle setting.  This is what is so great about the
> DZ.  The OS is fairly limp and useless until you get past 1/3 throttle. 
> At
> half throttle it comes alive, and at 5/8 throttle to full throttle, there 
> is
> little difference in output.  I think this is one of the major differences
> between two cycle and four.
>
> Power:  The OS does ok, but the DZ is far more powerful.  Maybe I need 
> more
> time on the OS before a fair comparison.  I have a gut feeling however, 
> from
> running this and watching other OS owners over the years, that the DZ
> dominates in power.
>
> Weight:  OS with ES muffler is probably 3-4 ounces lighter than a DZ with
> similar muffler.  But I think the DZ might be equivalent weight with a
> Hatori short pipe.  Not sure.
>
> Fuel requirements:  DZ runs best on one type and brand of fuel:  Cool 
> power
> 30% heli.  This is expensive stuff, and is my major gripe with the DZ. 
> The
> OS ran outstanding with 15% sport fuel.  For economy, you cannot beat 
> this.
>
> Smoke trail:  DZ has a thick smoke trail with CP 30%.  This OS had fair
> amount of smoke, but I expect it to decrease as I lean in.  None of OS' 
> that
> I see at contests have a heavy smoke trail.
>
> Overall preference:  This is a little tough because the DZ performs better
> for pattern, but the OS is probably good enough.  Greg Frohreich flies 
> very
> well with his OS, and until I can fly better, I wonder if I need a better
> engine.  Still, the DZ is a pleasure to run, with exception of the 
> expensive
> fuel.  I choose the DZ as my preference, but I like the OS for the 
> positive
> characteristics I mentioned.
>
>
> David
>
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