Bud- Irony that your great tuning advice comes on the same day as the forwa
rding of the Pipistrel item on their being selected as the launch company f
or the 912 Injection S engine!
Best,
Fred
________________________________
From: owner-europa-list-server@matronics.com on behalf of Bud Yerly
Sent: Wed 3/7/2012 7:38 PM
Subject: Re: Europa-List: Rough running 912S
Richard,
There are many things which can cause this problem and you are on the right
track. Rarely does a new Rotax need any tuning, but we tune them anyway h
ere at Custom Flight, as the factory doesn't quite center speck the engine
to what I call sewing machine smooth... In fact on the last three engines,
my fillings hurt from the factory tune. Not rough, but not right.
Please check your throttle cables are working together. I will not cut the
cables as the slightest of binding causes a draggy cable. Some use solid
cables, I have a bird flying 10 years on the same stock cables and it still
works like a charm. Check the plugs are all basically the same with no he
avy black soot or white hot deposits. A nice grayish brown look is right.
Next is the carb balance. We use dual manometers supplied by Rotax and m
echanically set the idle stops using the maintenance manual procedures, the
n we pneumatically balance the carbs until each carb is exactly the same pr
essure using the Rotax tuning method. Reconnect the crossover tube and all
should be smooth up to 4000 RPM. If you still have a rough spot, move the
needles to the third position.. At full throttle, and all is well, and whe
n at 3500 or below it runs rough on the ground please look at your carb mix
ture. For operations at sea level to 1500 feet field elevations we have fo
und setting the carb needle at the third position for both carbs does best
at clearing this rough area. The factory sets one carb normally at position
2 on the needle and the other on three. This third position is a bit ric
her and at part load we get better running at part throttle. If you have
EGT, note the changes on your EGT from side to side.. You can tell if it i
s too rich at 4000 RPM if you pull the choke out 1/4 inch and the engine ru
ns rough and wants to die as (believe it or not) the enrichening circuit (w
e call the choke) only works at near idle conditions and actually leans at
4000 RPM. If the engine smoothly increases or steady's, then your as rich
as you want. I didn't believe this until Kerry at Lockwood showed me on ou
r 914. Pretty neat.
If your mag drop is 300 or slightly more, you have a mixture problem. I kn
ow, it sounds stupid, but it is true. You may be a bit lean and moving the
needles to a richer setting may be necessary. I'm sure you're happy to no
te I have you taking the carbs apart a lot. But once set, I never have tou
ched mine in three years.
The carb heaters are not the problem, but check for an intake manifold leak
at the rubber gaskets as you said. Of course it will be easy to tell if y
ou have a manifold leak if you are using the dual Rotax carb balancing tool
with the gauges. I do not use the electric models. Close the in line val
ves to get the needles reasonably steady. Good advice has been given to wa
tching your intake plenum coming loose and checking for leaks as it causes
roughness in the lower 4-5000 RPM area.... .
Do clean the jets after the engine has sat for a long while for sure and ru
n the required check of the float bowl plunger so that it shuts off well.
Clean with solvent and low pressure air, not a piece of safety wire which w
ill scratch the jets and change your settings. Cleanliness in your tank an
d fuel lines is a must. I don't even start an engine until flushing the ta
nk at least three times with fuel, changing the filters in between and agai
n before test flying.
If she's still running rough look at ignition. Plugs should be clean, so c
heck your color and compare left side to right.
Hook a timing light to each spark plug lead and idle the engine using a hel
per to keep you safe. Watch the light and look for a miss in a cylinder.
You may have a bad coil, unlikely in a new engine, but it has happened.
Finally, if you have a fixed pitch prop (especially a Warp Drive) and you t
hrottle back in flight above 80 KIAS, the prop, when windmilling (being dri
ven by the wind) from high speed sets up a nasty noise and bit of vibration
. It is just like compression braking, and the 912S and gearbox combo with
this prop will tend to vibrate. This is the gear box lash and turbulence
off the prop making the nasty noise and bit of vibration. This is quite st
artling to the new Europa passenger. The Airmaster AP332 will also set u
p a vibration when compression braking in a rapid descent by moving the pro
p from cruise to climb at low power, as the blade change to a flatter setti
ng sets up a bit of turbulence... When doing a speed run at cruise of about
140 KIAS, I rarely move the prop to climb with the power set below 31 inch
es because it scares the customers with the sound change and vibration. Th
e comment is usually "is it supposed to do that!".
Keep us posted. You're on the right track.
Regards,
Bud Yerly
Custom Flight Creations, Inc.
www.customflightcreations.com <http://www.customflightcreations.com/>
(813) 653-4989
----- Original Message -----
From: Richard Iddon <mailto:riddon@sent.com>
To: europa-list@matronics.com
Sent: Wednesday, March 07, 2012 2:46 PM
Subject: Re: Europa-List: Rough running 912S
Hi Guys.
Fuel was drained before layup, bowls dropped and cleaned out. Engine
was l
eft with carbs at full throttle, i.e. minimum tension on springs. Carbs hav
e been re-balanced before test flight. Ran perfectly on the ground.
I have rotax permanent carb heaters fitted so that should eliminate
possib
ility of ice, (I hope!) although humidity was very high for this particular
flight. I had to wait for fog to clear before flight and temperature and d
ew point were both 7deg.
I guess I will pull the carbs off, check the sockets and diaphragms,
ensur
e float bowl vent pipes are OK. Incidentally, I replaced all the fuel pipes
, including the vent pipes, at layup.
Will report back if progress is made.
Richard Iddon.
On 7 Mar 2012, at 08:31, PHILLIPS I wrote:
> Hi Richard
> I would check the free movement of the throttle cables especially if
they
> have been under tension from the return springs for a year, Have you
don
e a carb sinc? also fuel left in float chambers will evaporate and leave a
gum like deposit
> in the bowl, its worth dropping the bowls for a check,
> good luck
> Ivor
>
> On 7 March 2012 08:10, david park <dpark748@hotmail.co.uk> wrote:
>
> Weather conditions. - carb ice?
>
> Sent from my iPhone
>
>
> On 7 Mar 2012, at 05:07, klinefelter.kevin@gmail.com wrote:
>
> >
> > Where do I look next?
> > Carbs.
> > Kevin
> >
> > On Mar 6, 2012, at 1:23 PM, Richard Iddon <riddon@sent.com> wrote:
> >
> >>
> >> My 912S hasn't run for almost 12 months. It started and ran well
on g
round runs. Test flight was OK although there was some 'plucking'. Since th
en I have flown three more times and am finding that the engine runs fine a
t full revs or climb settings but when I back off at the top of the climb,
it splutters and coughs a bit and runs quite roughly as if it is missing a
bit. Doesn't fill me with confidence. I have pulled the plugs and they seem
fine, nice even grey colour, no oily plugs. Where do I look next?
> >>
> >> Richard Iddon
> >>
> >> G-RIXS
> >>
> >>
> >>
> >>
> >
> >
> >
> >
> >
>
>
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