Model Forum / Radio Controlled / Air Models / July 2008

I have no personal experience of tuning an ST.

Their web site (and many other people who have
posted here since 1995) recommends that the
hole in the spraybar be straight down:

http://www.supertigre.com/faq/product-faq.html

As often happens with tuning, people disagree
about what works and what doesn't work.  In
my view, you should feel free to experiment
and report your results here so that the peanut
gallery can learn from your mistakes.  :o)

                Marty

Start with the spray bar straight. It may take a tiny twist later but
that is usually your last resort.
The most important thing you can do, in particular with the ST51, is
switch to an OS-8 glow plug. The ST plugs are basically junk.
I fought with my ST51 for months before I came to that simple
solution. It simply wouldn't mid-range well.
Now it runs great, hardly ever needs adjustment, and starts easily.

Good luck,
 --Mark

A couple of weekends ago we took apart a ST45 carb.  Seems to me(<-that was
a disclosure about accuracy), the spray bar was at 4 or 5 o;clock when
viewing it from the needle end.  It looked to be pointing right down the
throat of the engine.  I have one I could go take apart and look at if ya
want? Use an OS #8
mk

The spray bar position is considered to be a tuning adjustment also.  In my
club we would swap the ST carb for an OS.  Then they would run like a raped
ape.

Is it a true 2 needle carb, and not a high speed needle and air bleed
valve?

If the spray bar changes do not do the trick, and it is a two needle carb,
you might be able to take a trick from the older Fox engines.

The instructions told the user to modify the profile of the low speed needle
to adjust the midrange.

The told you (and they were right) to chuck it into a drill, and turn it
fast, and put some sandpaper to it, either on the tip to "dull it" or the
"shoulder" where the angle met the full diameter of the shaft.

I think (it has been a while) if the midrange was lean, you sand a small
radius on the shoulder.  It does not take much, and if you go too far, be
prepared to buy a new needle and try again. DAMHIKT!
<g>

Hi Ted,
My experience with the 5 ST engines that I have owned/own has been varied.
I have never experienced that moving the spray bar has made a difference in
the performance of the Super Tigre engines. I have also tried placing a
brass ferral in the carb throat to decrease the intake diameter with no
positive effect.
Today I have two G-51 that are three years old and they both misbehave on a
regular basis. One is on a Seamaster and I have the low needle at 8 plus
turns out to keep the low end and mid transition from going lean. The other
G-51 is on a trainer and is always full of surprises. I don't know if these
engines are sensitive to barometric pressure or the alignment of the
planets. Some days they run very acceptable and other days they are
threatening to stall during transitions.
I have a G-45 and a 40 (Italian made) that run like clocks with no issues
what so ever.
I did own ( and now returned to Tower Hobbies with full refund) a 61 size
engine that ate three planes.

I see others peoples responses indicate that they need a lot of break-in. If
more that three gallons of fuel does not qualify for break-in, then I need
to sell these G51's to some unsuspecting person on Ebay and go buy some
magnum XLS-46's.
I have not replaced my temperamental ST G-51's because I am frugal and I
like a dead stick challenge at least twice a week. If I were to purchase new
engines I would not purchase a ST again. I own OS, GMS, Magnum, Jett and
Weston engines and do not have the trouble that I have with the two G-51's.

On a side thought, maybe the issue with the G-51's are a quality issue with
machined surface tolerances and are on the margin of acceptable dimensions.
Does anybody know what happens when the crank intake area under the carb
opening and the inside wall of the crank case get leaky?

Thanks for reading
RCS