Today's Message Index:
----------------------
1. 03:05 AM - Re: Rotax 912 ul engine problems (fgoggio@yahoo.com)
2. 03:49 AM - Re: RotaxEngines-List Digest: 17 Msgs - 06/17/12 (James Meade)
3. 03:53 AM - Re: RotaxEngines - Rotax 912 ul engine problems (MacDonald Doug)
4. 04:17 AM - Re: Rotax 912 ul engine problems (Thom Riddle)
5. 04:46 AM - Re: Rotax 912 ul engine problems (Catz631@aol.com)
6. 06:16 AM - Re: Rotax 912 ul engine problems (Scott DeMeyer)
7. 07:24 AM - 912ul miss (egp8111)
8. 07:29 AM - Re: 912ul miss (Blumax008@aol.com)
9. 01:00 PM - Re: Rotax 912 ul engine problems (Roger Lee)
10. 01:07 PM - Re: 912ul miss (Roger Lee)
11. 01:46 PM - Re: Re: Rotax 912 ul engine problems (Craig Payne)
12. 02:03 PM - Re: Rotax 912 ul engine problems (Roger Lee)
13. 02:47 PM - Re: Re: RotaxEngines-List Digest: 17 Msgs - 06/17/12 (=?ISO-8859-1?Q?J=F3hann_J=F3hannsson?=)
14. 03:37 PM - Re: Rotax 912 ul engine problems (Gtblu)
Message 1
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| Subject: | Re: Rotax 912 ul engine problems |
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Message 2
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| Subject: | Re: RotaxEngines-List Digest: 17 Msgs - 06/17/12 |
What happens when you do a mag check when the engine is running rough? If
you have CHT or EGT gaugges, what are they showing when running rough?
What happens aboute the rough onset altitude, or do you get it above
that? The engine smooths out by itself when running at lower altitude?
Does the roughness correspond with how hard the engine is worked, such as
on a hard climb as opposed to an easy climb? What happens if you climb at
WOT through the normal onset altitude, or do you already?
Message 3
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| Subject: | Re: RotaxEngines - Rotax 912 ul engine problems |
I say this every time someone has a rough running engine.- =0A-=0ACheck
to make sure the-enrichener arms-are closing all the way.- =0AIt is
counter intuitive, but on a Bing carb, a partially open enrichener acts lik
e =0Aan air bleed-at higher RPM and creates a lean condition and thus rou
gh =0Arunning.- I got this from Dean Vogul from Lockwood and it fixed my
problems =0Aduring- initial installation of my 80hp rotax.- I was exper
iencing roughness and =0Aloss- of power at 3600-4200 RPM and above-unti
l I adjusted my enrichener =0Acable to give me complete closure.The arms-
don't have to be off the stops=0Amuch to create a problem.=0A-=0ADoug M
=0ACH-701, 912UL=0ANW Ontario, Canada=0A=0A=0ATime: 06:21:34 AM PST US=0AFr
om: =?ISO-8859-1?Q?J=F3hann_J=F3hannsson?= <joeing701@simnet.is>=0A
Subject: RotaxEngines-List: Rotax 912 ul engine problems=0A=0A=0AHello list
members.=0A=0AWe really need your- expert help regarding a Rotax 912 ul
80 hp engine- =0Aproblem my friend has been dealing with for the past-
three years or- =0Aever since he bought the plane.=0A=0AMy friend bought
this- Kitfox II aprox. 1990 model from USA and has- =0Abeen trying to s
olve a rough running engine problem, and is about to- =0Agive up on the p
roject.=0A=0AHere is the symptoms:=0A=0AEngine starts perfectly and runs on
both mags with a drop within 100- =0Arpm. When airborne the rough runnin
g starts around 3500-4500.- =0AEverything shakes very violently and aircr
aft looses altitude. Most- =0Aoften you can give it full power to continu
e flying, but when power is- =0Areduced, the shaking starts again.
Message 4
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| Subject: | Re: Rotax 912 ul engine problems |
One thing I have found to cause rough running is poor connection between the spark
plug wires and spark plug connector/cap. I've run across this several times.
Make sure all are screwed in all the way clock-wise. After the first time
I encountered this, I always check them on each condition inspection and mark
the intersection with torque-seal or equivalent so they can be visually checked
in the future.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
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| Subject: | Re: Rotax 912 ul engine problems |
Johann,
As Frank mentioned ,we too had a similar problem in a Paradise P-1. It
would be rough in mid range.It was silky smooth so long as full power was
applied (as in climbout) but upon power reduction the roughness would start
and the airplane would vibrate like hell ! At one point during
troubleshooting, I even shut the engine down and glided the airplane thru various
speeds
to see if it was airframe related ...it wasn't.
It drove us nuts trying to find it. We changed props,tightened
mounts,checked/synced carbs,etc,etc. Finally we sent the gearbox off to Lockwood
for
a re shim/rebuild as a last resort and that did it ! The engine did not
have that much time and I would have sworn that was not the problem but it
fixed it !
My Kitfox had a similar problem but I was able to fix it by replacing the
throttle cables as one of them was apparently slightly sticking at mid
range throwing the carbs out of balance. Check the "swivel" nuts on the carbs
for sticking also.
That is my two cents.
Good luck !!
Dick Maddux
Milton,Fl
Message 6
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| Subject: | Re: Rotax 912 ul engine problems |
Same exact problem here. Rebuilt carbs several times and changed many ignition
components and nothing worked. After months of troubleshooting I gave up and flew
the plane to a Rotax dealer. He rebuilt the gearbox and the problem went away.
I had about 500 hours on the gearbox, 80HP Rotax.
________________________________
Message 7
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I know this issue has been worked over a few times on the forum but I cant seem
to find anything that matches my situation. Here's the deal, the 912 starts
fine after warm up on the initial mag check it has about a 150-200 rpm drop on
either mag at 4000 rpm. In flight it has an occasional miss at 5000rpm, some
more notable than others. It also runs rough between 3000 and 4000 rpm not
missing just rough feeling. After I land I can check the mags again and they
only have a drop of about 50 rpm on either side. I've pneumatically balanced
the carbs and they are dead on at 2500 rpm. The carbs have been cleaned and adjusted.
new plugs etc. Also today I flew through a very light rain shower and
the engine began to run notably rough at 5000rpm. After I left the area of
rain it cleared up. Carb ice ? I do not have the carb heat box installed.
Any ideas?
Thanks EG
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Message 8
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Possible leads. Tie it down or chock it good in a dark hangar at night and
see if you see any fireworks are visible from the spark plug leads. May be
breaking down at higher rpms or causing occasional trouble. Just a guess.
In a message dated 6/18/2012 10:24:54 A.M. Eastern Daylight Time,
egp8111@aol.com writes:
--> RotaxEngines-List message posted by: "egp8111" <egp8111@aol.com>
I know this issue has been worked over a few times on the forum but I cant
seem to find anything that matches my situation. Here's the deal, the
912 starts fine after warm up on the initial mag check it has about a 150-200
rpm drop on either mag at 4000 rpm. In flight it has an occasional miss
at 5000rpm, some more notable than others. It also runs rough between 3000
and 4000 rpm not missing just rough feeling. After I land I can check the
mags again and they only have a drop of about 50 rpm on either side. I've
pneumatically balanced the carbs and they are dead on at 2500 rpm. The
carbs have been cleaned and adjusted. new plugs etc. Also today I flew
through a very light rain shower and the engine began to run notably rough at
5000rpm. After I left the area of rain it cleared up. Carb ice ? I do not
have the carb heat box installed.
Any ideas?
Thanks EG
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=375987#375987
Message 9
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| Subject: | Re: Rotax 912 ul engine problems |
Hi All,
Gearbox's can certainly cause engine roughness, but I personally find the owners
with Vernier type throttle cables to have more issues than others. The thicker
wire to these type cables causes them to slightly stick in the sheath and when
you operate the throttle one carb won't go back to exactly the same place.
This makes one side of the engine try to run at let's say 5000 rpm while the
other side tries to run at 5300 rpm. This opposing action makes things rough and
not good for the long term health of the engine. This can make the carb sync
procedure an headache too.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
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Message 10
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Hi EGP,
What are the plugs gapped at? They should be between .023 - .027. The wider gap
for the hotter months. If the gap is too narrow especially in the summer you
will get bigger mag drops and possible roughness.
The second item is 2500 rpm is too low to do a very good balance. If you balance
at 2500 and then run the rpm up to 4000 you will find that they will be off
again. 2500 is too close to the idle circuit range and just doesn't flow enough
fuel/air to get set up well. Check the plug gaps, apply the thermal conducting
paste and not anti seize and then re-balance the carbs at 3500-4000. I would
bet your engine will run even smoother. Depending on how your air cleaner is
set up you may have taken on a little water, but no big deal as it usually runs
through the system especially with 91 oct with ethanol.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
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| Subject: | Re: Rotax 912 ul engine problems |
> The thicker wire to these type cables causes them to slightly stick in the
sheath and when you operate the throttle one carb won't go back to exactly
the same place.
Are you referring to vernier throttles where the cables spit at the
throttle. McFarLane makes this one:
http://www.mcfarlane-aviation.com/Details.aspx?Article=199
I don't see how what you are describing could happen with a conventional
vernier throttle where there is only a single cable that connects to an
external splitter.
-- Craig
Message 12
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| Subject: | Re: Rotax 912 ul engine problems |
Hi Craig,
Just like that one. What happens is the sheath is metal on the inside and some
times they get a slight corrosion and or some throttle setups have a little too
much bend in one cable. It only takes about 1/16" with a little friction in
a long cable with too tight a bend to cause the cable to not go back exactly to
the same position. If you have a cable setup with small 1mm- 1.2mm cable then
the springs on the carbs will almost always pull the cables back exactly to
the same place every time. With a thick cable with a little bend the springs sometimes
don't have quite enough tension to pull every last little bit of cable
taught. The guys with the springs on the opposite side of the throttle arm that
pull the cable back to idle cab be at times even worse. This condition will
show up in a carb sync. Sync the carbs and then pull them back and forth 3-4
times and they should go back to where you set them the first time. If they seem
to keep getting out of adjustment and you have a Vernier cable then you know
what the issue is. I use my finger on the throttle arms to make sure the Vernier
type cable always comes completely back out and make sure any little friction
isn't a player in the sync job.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=376025#376025
Message 13
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| Subject: | Re: RotaxEngines-List Digest: 17 Msgs - 06/17/12 |
Hello James.
My friend did not dare do the mag check during this situation. The
plan was to try it the next flight. EGT show the same temp. CHT analog
meters not very steady to judge any difference. We have not tried
climbing to an altitude higher than 1500 feet. Does not seem to change
during climb or when under hard work. Last time we did the test, the
plane climbed almost 1400 feet/min and with no hesitation. Roughness
started when we leveled off and reduced the throttle below 5000 rpm.
Thank you for your help.
Johann G.
Iceland.
On 18.6.2012, at 10:48, James Meade wrote:
> >
>
> What happens when you do a mag check when the engine is running
> rough? If you have CHT or EGT gaugges, what are they showing when
> running rough? What happens aboute the rough onset altitude, or do
> you get it above that? The engine smooths out by itself when
> running at lower altitude? Does the roughness correspond with how
> hard the engine is worked, such as on a hard climb as opposed to an
> easy climb? What happens if you climb at WOT through the normal
> onset altitude, or do you already?
>
>
Message 14
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| Subject: | Re: Rotax 912 ul engine problems |
Hi Johanne, I had a vibration problem at similar revs to you (5000) but not as
bad in a 912uls. Having tried everything on the engine and gearbox I focused on
the prop (thanks to Roger). It turned out to be the bolt lengths on the prop
were too long by a fraction of a millimeter thus torquing the bolts to the end
of their thread. Different atmospheric conditions allowed the prop hub to contract
and expand, making the problem intermittent. A new set of correct length
bolts solved the problem, however a whole new prop was fitted which in fact
showed every prop/engine combination has its own vibration band, NOW being at
about 4200 revs. Thats another topic!
Cheers
Geoff Bell
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