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tleiss(at)earthlink.net
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 Posted: Thu Mar 01, 2007 4:56 pm Post subject: 912 Carbs |
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Looking for some help.
[quote]
My Rotax 912UL is running very rough at Idle. Also have fuel running out the vent tubes unless idle is above 2400rpm. I have rebuilt both carbs (Bing 64) with kits from Bing. Initial set-up as described in the Bing instructions. I have synchronize the carbs with duel vacuum gauges. However, adjusting the mixture screws has virtually no effect in RPM or the vacuum gauge readings. Ignition is working fine, all new plugs. All new connectors and good drop-offs when switching A or B (Mag Check).
I have compared my engines performance with two other 912 equipped planes on the field. Mine is much rougher at low and medium speeds.
One question is if the Carb piston vents go towards the intake manifold (as I have them) or the intake.
Engine has 200 hours (192 by previous owner), 1 hour flight time since I've owned it and the rest are ground runs trying to get it running right.
Thanks,
Todd Leiss
Kitfox IV Speedster
N926JB
Merritt Island Florida
[b]
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Thu Mar 01, 2007 7:07 pm Post subject: Re: 912 Carbs |
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Hi Todd,
Question: Are both carbs actting up in the same way?
Those vents you describe on the carb throat edges are actually inlets. They must face out towards the air cleaner side or you will have the problems as you describe. These intakes help work the diaphram in the top of your carb for pressure changes.
If this was the problem your home free, if not:
One of the things you need to check is your fuel pump pressure. There is a new service bulletin out on certain serial numbered engines that they want these pumps replaced. The symptoms are as you describe. The max pressure (without the manual in front of me) is 5.6 psi and some of these pumps are putting out in the 9psi range.
This type of pressure will cause what you have described. There is a replacement program as I understand it.
Your mixture screw should be set at 1.5 turns and left alone. Then you should set the carb's idel screw with the engine off and then while it is running.
My bet is that your carbs are facing the wrong way.
Good luck!
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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daveaustin2(at)primus.ca
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| Posted: Thu Mar 01, 2007 7:21 pm Post subject: 912 Carbs |
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Certainly sounds as if you have a flooding condition. What fuel pressure do you have to the carbs? anything beyond 4 lbs will overcome the needle valves. Vent tubes should be in a place which will sense normal air pressure, not near carb intake.
Dave Austin 601HDS - 912, Spitfire Mk VIII
[quote] ---
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tleiss(at)earthlink.net
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| Posted: Thu Mar 01, 2007 9:30 pm Post subject: 912 Carbs |
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Some more info on my carb problem:
My vent tubes are the proscribed length (about 4 inches), and tucked under
the float bowl spring clip.
I have new Boots or Flanges.
Vents under Carb inlets are free. Carbs are facing the correct way.
Synchronized by the Lockwood method (two Vacuum gauges) adjusting the
throttle cables as described in a "power-up" article.
On the bottom of the Carb slide (with long needle valve set at proscribed
clip position) there are two vent holes. Do these face the air filter or
Intake manifold (as I have them)?
I have a new (Jan 07) Fuel pump from Lockwood. I had ignition issues,
which I solved, but around the same time my old fuel pump started to leak.
The carbs didn't have the fuel running out the vents before the new pump,
but it never occurred to me that the pump could be the problem. This may
very well be the issue. I will definitely check with Lockwood tomorrow
concerning the fuel pressure.
Keep the wonderfully helpful cards and letters coming.
All the Best,
Todd
| Quote: | [Original Message]
From: Roger Lee <ssadiver1(at)yahoo.com>
To: <rotaxengines-list(at)matronics.com>
Date: 3/1/2007 10:15:21 PM
Subject: RotaxEngines-List: Re: 912 Carbs
Hi Todd,
Question: Are both carbs actting up in the same way?
Those vents you describe on the carb throat edges are actually inlets.
They must face out towards the air cleaner side or you will have the
|
problems as you describe. These intakes help work the diaphram in the top
of your carb for pressure changes.
| Quote: |
If this was the problem your home free, if not:
One of the things you need to check is your fuel pump pressure. There is
a new service bulletin out on certain serial numbered engines that they
|
want these pumps replaced. The symptoms are as you describe. The max
pressure (without the manual in front of me) is 5.6 psi and some of these
pumps are putting out in the 9psi range.
| Quote: | This type of pressure will cause what you have described. There is a
replacement program as I understand it.
|
| Quote: | Your mixture screw should be set at 1.5 turns and left alone. Then you
should set the carb's idel screw with the engine off and then while it is
|
running.
| | - The Matronics RotaxEngines-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?RotaxEngines-List |
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oneniner
Joined: 08 Feb 2007
Posts: 4
Location: Montana
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| Posted: Thu Mar 01, 2007 10:00 pm Post subject: 912 Carbs |
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Check with Lockwood, but I bet the new pump has caused the problem. The Jabiru engines commonly have this problem, because their fuel pump is not consistent in output pressure.
I have no personal experience with this, but what I have read (especially on the Jabiru forum) is that the Bing needs a relatively low fuel pressure, something like 5 or 6 psi max. If it is too high, the fuel will force past the needle valve and raise the float level too high. It will run very rich, and leak fuel out the vents as you describe. There apparently are different needle valves available, and using the wrong one can cause the same problem even with fuel pressure within limits.
This will be an easy problem to fix, by making sure you have the proper fuel pressure, and the proper needle and seat in the carbs.
Again, I am sure Lockwood can provide the specific help you need.
Gary
Todd Leiss wrote: [quote] | Quote: | --> RotaxEngines-List message posted by: "Todd Leiss" <tleiss(at)earthlink.net> (tleiss(at)earthlink.net)
Some more info on my carb problem:
My vent tubes are the proscribed length (about 4 inches), and tucked under
the float bowl spring clip.
I have new Boots or Flanges.
Vents under Carb inlets are free. Carbs are facing the correct way.
Synchronized by the Lockwood method (two Vacuum gauges) adjusting the
throttle cables as described in a "power-up" article.
On the bottom of the Carb slide (with long needle valve set at proscribed
clip position) there are two vent holes. Do these face the air filter or
Intake manifold (as I have them)?
I have a new (Jan 07) Fuel pump from Lockwood. I had ignition issues,
which I solved, but around the same time my old fuel pump started to leak.
The carbs didn't have the fuel running out the vents before the new pump,
but it never occurred to me that the pump could be the problem. This may
very well be the issue. I will definitely check with Lockwood tomorrow
concerning the fuel pressure.
Keep the wonderfully helpful cards and letters coming.
All the Best,
Todd
| Quote: | [Original Message]
From: Roger Lee <ssadiver1(at)yahoo.com> (ssadiver1(at)yahoo.com)
To: <rotaxengines-list(at)matronics.com> (rotaxengines-list(at)matronics.com)
Date: 3/1/2007 10:15:21 PM
Subject: Re: 912 Carbs
--> RotaxEngines-List message posted by: "Roger Lee" <ssadiver1(at)yahoo.com> (ssadiver1(at)yahoo.com)
Hi Todd,
Question: Are both carbs actting up in the same way?
Those vents you describe on the carb throat edges are actually inlets.
|
They must face out towards the air cleaner side or you will have the
problems as you describe. These intakes help work the diaphram in the top
of your carb for pressure changes.
| Quote: | If this was the problem your home free, if not:
One of the things you need to check is your fuel pump pressure. There is
|
a new service bulletin out on certain serial numbered engines that they
want these pumps replaced. The symptoms are as you describe. The max
pressure (without the manual in front of me) is 5.6 psi and some of these
pumps are putting out in the 9psi range.
| Quote: | This type of pressure will cause what you have described. There is a
|
replacement program as I understand it.
| Quote: | Your mixture screw should be set at 1.5 turns and left alone. Then you
|
should set the carb's idel screw with the engine off and then while it is
running.
[Original Message]
From: Roger Lee <ssadiver1(at)yahoo.com> (ssadiver1(at)yahoo.com)
To: <rotaxengines-list(at)matronics.com> (rotaxengines-list(at)matronics.com)
Date: 3/1/2007 10:15:21 PM
Subject: Re: 912 Carbs
--> RotaxEngines-List message posted by: "Roger Lee" <ssadiver1(at)yahoo.com> (ssadiver1(at)yahoo.com)
Hi Todd,
Question: Are both carbs actting up in the same way?
Those vents you describe on the carb throat edges are actually inlets.
|
0 [b]
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