 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
JetPilot
Joined: 10 Jan 2006
Posts: 1246
|
 Posted: Thu Aug 23, 2007 8:47 am Post subject: New Rotax 912-S Running Rough... |
 |
|
I have a new Rotax 912-ULS that has been giving me some problems. This is strange, so I will give you guys the complete history.
I got the engine new and it ran perfect for the first 10 hours. After 10 hours it started to run very rought at idle, but would be fine once I flew, idle missing dissapeared. About 5 hours later, the missing at idle got worse and lasted longer so I replaced the plugs and the engine was perfect again  ( Note - The old plugs were WHITE, no aluminum or metal, but white colored almost looked new , my egt's were running 1475 degrees thoughout the power range ) My fuel usage was also a very low 3.5 gallons per hour at 4500 RPM cruise.
With 10 hours on the new plugs, my rough running at idle started to show up again. Once I took off, it was fine until the next day. Over the next 10 hours or so the problem at idle got worse, it started to run rough again even when warm. I kept flying, and finally the missing started to be just barely detectable in flight, and much worse on the ground, so I decided it was time to do something. All the plugs were again WHITE, so I raised the needles one notch from factory setting to make it richer. I flew it once, EGT's went down 50 degrees, but soon it started to miss, and not want to run at all. I checked the plugs and they were VELVET BLACK, as black as black can be  How can raising the needle one notch make the the mixture so rich that it will not run ???
General notes, the carbs are balanced perfectly. Fuel filter is good, when I pulled the bowls, they were clean enough to drink out of. The engine is only a year old with not quite 50 hours on it now. EGT's have always been in the 1400's, and matched on both sides. CHT's have also always been right in limits, never a problem with any temps.. I see evidence of fuel comming out ONE carb vent, 4 inch long vent terminated at carb body, but lockwood tells me this happens and is normal. It is not excessive, but I see the fuel residue and discoloration there where the fuel has been hitting the spark plug / cylender. The engine is propped for 5300 RPM climb and 5400 RPM wide open cruise. Any ideas what could be causing these problems ??
Thanks,
Mike
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
|
| Back to top |
|
 |
kerrjohna(at)comcast.net
Guest
|
| Posted: Thu Aug 23, 2007 11:17 am Post subject: New Rotax 912-S Running Rough... |
|
|
Mike, I went through a lengthy adjustment period with my 912ul this spring. It has 760 hrs but suddenly started acting funny at idle.
I detailed the steps taken for Lowell Fitt but failed to save a copy of them. Perhaps he has that saved and can forward it to you. Or given some time I can recreate it.
Flew this morning, dead calm, cool almost autumn air. The engine is running better than ever. The key to understanding the bing carburetor is remembering that there are 3 (4) fuel circuits that interrelate and overlap at different rpms.
John Kerr
[quote]-------------- Original message --------------
From: "JetPilot" <orcabonita(at)hotmail.com>
| Quote: | --> Kitfox-List message posted by: "JetPilot"
I have a new Rotax 912-ULS that has been giving me some problems. This is
strange, so I will give you guys the complete history.
I got the engine new and it ran perfect for the first 10 hours. After 10 hours
it started to run very rought at idle, but would be fine once I flew, idle
missing dissapeared. About 5 hours later, the missing at idle got worse and
lasted longer so I replaced the plugs and the engine was perfect again (
Note - The old plugs were WHITE, no aluminum or metal, but white colored almost
looked new , my egt's were running 1475 degrees thoughout the power range ) My
fuel usage was also a ve ry low 3.5 gallons per hour at 4500 RPM cruise.
With 10 hours on the new plugs, my rough running at idle started to show up
again. Once I took off, it was fine until the next day. Over the next 10 hours
or so the problem at idle got worse, it started to run rough again even when
warm. I kept flying, and finally the missing started to be just barely
detectable in flight, and much worse on the ground, so I decided it was time to
do something. All the plugs were again WHITE, so I raised the needles one
notch from factory setting to make it richer. I flew it once, EGT's went down
50 degrees, but soon it started to miss, and not want to run at all. I checked
the plugs and they were VELVET BLACK, as black as black can be How can
raising the needle one notch make the the mixture so rich that it will not run
???
General notes, the carbs are balanced perfectly. Fu el fil ter is good, when I
pulled the bowls, they were clean enough to drink out of. The engine is only a
year old with not quite 50 hours on it now. EGT's have always been in the
1400's, and matched on both sides. CHT's have also always been right in limits,
never a problem with any temps.. I see evidence of fuel comming out ONE carb
vent, 4 inch long vent terminated at carb body, but lockwood tells me this
happens and is normal. It is not excessive, but I see the fuel residue and
discoloration there where the fuel has been hitting the spark plug / cylender.
The engine is propped for 5300 RPM climb and 5400 RPM wide open cruise. Any
ideas what could be causing these problems ??
Thanks,
Mike
--------
"NO FEAR" - If you have no fear you did not go as fast as you could
have !!!
Kolb MK-III Xtra, 912-S
&g t; |
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
kitfoxmike
Joined: 05 Dec 2006
Posts: 373
|
| Posted: Thu Aug 23, 2007 11:27 am Post subject: Re: New Rotax 912-S Running Rough... |
|
|
Yup, three different circuits that overlap each other. I would put the needles back where they where and then get some carb cleaner and remove the bowls, then remove each circuit, idle, midrange, and the main. One at a time, and force the carb cleaner into each, with air blown afterwards. You might be surprised at what happens afterwards. I make it a habit to do this at an oil change or 50 hrs. Mine runs better than ever.
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
tleiss(at)earthlink.net
Guest
|
| Posted: Thu Aug 23, 2007 5:04 pm Post subject: New Rotax 912-S Running Rough... |
|
|
I had a problem with rough running at Idle. Went thought all of the steps
you have. But, Whit I finally found was that the fuel pressure from the
Fuel pump was too high. The fuel pressure was overcoming the float
needles and flooding the carbs. Above ~ 2500 rpm the problem went away.
(I used a Vacuum/fuel pressure gauge to check it). I put a fuel pressure
regulator between the pump and the carbs and haven't had a problem since
(25 hours).
Todd Leiss
Model IV Speedster
912ul
| Quote: | [Original Message]
From: JetPilot <orcabonita(at)hotmail.com>
To: <kitfox-list(at)matronics.com>
Date: 8/23/2007 12:54:05 PM
Subject: New Rotax 912-S Running Rough...
I have a new Rotax 912-ULS that has been giving me some problems. This
is strange, so I will give you guys the complete history.
|
| Quote: |
I got the engine new and it ran perfect for the first 10 hours. After 10
hours it started to run very rought at idle, but would be fine once I flew,
|
idle missing dissapeared. About 5 hours later, the missing at idle got
worse and lasted longer so I replaced the plugs and the engine was perfect
again ( Note - The old plugs were WHITE, no aluminum or metal, but
white colored almost looked new , my egt's were running 1475 degrees
thoughout the power range ) My fuel usage was also a very low 3.5 gallons
per hour at 4500 RPM cruise.
| Quote: |
With 10 hours on the new plugs, my rough running at idle started to show
up again. Once I took off, it was fine until the next day. Over the next
|
10 hours or so the problem at idle got worse, it started to run rough again
even when warm. I kept flying, and finally the missing started to be just
barely detectable in flight, and much worse on the ground, so I decided it
was time to do something. All the plugs were again WHITE, so I raised the
needles one notch from factory setting to make it richer. I flew it once,
EGT's went down 50 degrees, but soon it started to miss, and not want to
run at all. I checked the plugs and they were VELVET BLACK, as black as
black can be How can raising the needle one notch make the the mixture
so rich that it will not run ???
| Quote: |
General notes, the carbs are balanced perfectly. Fuel filter is good,
when I pulled the bowls, they were clean enough to drink out of. The
|
engine is only a year old with not quite 50 hours on it now. EGT's have
always been in the 1400's, and matched on both sides. CHT's have also
always been right in limits, never a problem with any temps.. I see
evidence of fuel comming out ONE carb vent, 4 inch long vent terminated at
carb body, but lockwood tells me this happens and is normal. It is not
excessive, but I see the fuel residue and discoloration there where the
fuel has been hitting the spark plug / cylender. The engine is propped for
5300 RPM climb and 5400 RPM wide open cruise. Any ideas what could be
causing these problems ??
| Quote: |
Thanks,
Mike
--------
"NO FEAR" - If you have no fear you did not go as fast as you
could have !!!
|
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
JetPilot
Joined: 10 Jan 2006
Posts: 1246
|
| Posted: Sun Aug 26, 2007 6:09 am Post subject: Re: New Rotax 912-S Running Rough... |
|
|
I dont think its a fuel pressure problem, as its been running lean until I changed the needle position.
Mike
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
