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cristalclear13
Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia
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 Posted: Tue Jun 02, 2009 6:36 pm Post subject: strange sputtering |
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Decided to take my dad, who is visiting me, on a little cross country in my Kolb Mark II to Douglas, GA. I wanted to show him the WWII museum there but found out they are only open on Fridays and Saturdays once we got there.
We had had some fog in the morning but it burned off around 10:30am and so we headed out. When we got to Douglas and landed, I was about to turn the plane around and exit on the taxiway I just passed but when I started to turn and gave it a little more on the throttle it kind of sputtered and wouldn't rev up. I pulled it back and tried it again and it went fine. Then when I was parking her it did it again.
My carbs were sweating the front one more than the back. That isn't unusual in the hot weather we have though. On the front carb where the rubber socket is the carb had some black stuff along the edge where it fits into the socket (whereas my back carb was nice and clean in that area). I grabbed my screwdriver and tightened the clamp around the socket. It may have been a little loose. Perhaps it was sucking air?
We ate lunch, considered our options and then decided to start it up, if no problems then take off and go around the airport a bit. We didn't have any more problems so we headed home and didn't have any more symptoms of the sort. The afternoon thermals sure gave us an interesting ride home. I think I'm getting more used to it. I think I had my best landing yet with a full-size passenger when Dad and I got back to Waycross. 
Side note to George Alexander: Got your message...thanks.
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Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009 |
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mdnanwelch7(at)hotmail.co
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| Posted: Tue Jun 02, 2009 7:53 pm Post subject: strange sputtering |
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> My carbs were sweating the front one more than the back. That isn't unusual in the hot >weather we have though.> --------
| Quote: | Cristal Waters
Kolb Mark II Twinstar
Rotax 503 DCSI
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Christal C
Sounds as though you experienced the classic symptoms of "carb icing" C although from your description of the carb's sweating C you may have only developed condensation C not icing.
If your rpms are high C as they are in cruise C your engine can usually ride out the humidity's sweating condition. However C the moisture often presents itself on throttling back C as in the landing mode or taxiing.
It's not uncommon for some people to report their engines died on entering the traffic pattern(with a reduced power setting).
I'm not sure what you could do to minimize this tendency. Has anyone come up with a carb heat mechanism for Bing carbs??
Mike Welch
MkIII
Insert movie times and more without leaving HotmailŪ. See how. [quote][b]
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Wed Jun 03, 2009 2:45 am Post subject: strange sputtering |
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At 11:25 PM 6/2/2009, Mike Welch wrote:
| Quote: | > My carbs were sweating the front one more than the back. That isn't
unusual in the hot >weather we have though.> --------
Sounds as though you experienced the classic symptoms of "carb icing",
although from your description of the carb's sweating, you may have only
developed condensation, not icing.
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I spent some time chasing carb icing when the engine was reluctant to
increase from cruise to full throttle and was covered with condensation
when I landed. Turned out, though, it was not icing but simply running too
rich for the very hot humid day that it was... dropping the needle one
notch solved the problem.
| Quote: | I'm not sure what you could do to minimize this tendency. Has anyone
come up with a carb heat mechanism for Bing carbs??
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Somebody does make an electric carb heater for the Bings. It's a spacer
block that goes between the carb and the manifold. Since it heats the carb
body and not the air, you leave it turned on all the time without affecting
performance.
-Dana
--
Growing old is inevitable, but we can stay immature indefinitely.
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lucien
Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM
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| Posted: Wed Jun 03, 2009 5:15 am Post subject: Re: strange sputtering |
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| cristalclear13 wrote: | Decided to take my dad, who is visiting me, on a little cross country in my Kolb Mark II to Douglas, GA. I wanted to show him the WWII museum there but found out they are only open on Fridays and Saturdays once we got there.
We had had some fog in the morning but it burned off around 10:30am and so we headed out. When we got to Douglas and landed, I was about to turn the plane around and exit on the taxiway I just passed but when I started to turn and gave it a little more on the throttle it kind of sputtered and wouldn't rev up. I pulled it back and tried it again and it went fine. Then when I was parking her it did it again.
My carbs were sweating the front one more than the back. That isn't unusual in the hot weather we have though. On the front carb where the rubber socket is the carb had some black stuff along the edge where it fits into the socket (whereas my back carb was nice and clean in that area). I grabbed my screwdriver and tightened the clamp around the socket. It may have been a little loose. Perhaps it was sucking air?
We ate lunch, considered our options and then decided to start it up, if no problems then take off and go around the airport a bit. We didn't have any more problems so we headed home and didn't have any more symptoms of the sort. The afternoon thermals sure gave us an interesting ride home. I think I'm getting more used to it. I think I had my best landing yet with a full-size passenger when Dad and I got back to Waycross.
Side note to George Alexander: Got your message...thanks. |
Yet another reason I finally made my escape from the Gulf Coast to a place with cleaner air..........
It was rare for me when I lived in TX to land _without_ the carburettor bodies simply soaked with condensation, enough for it to be literally dripping down onto the float bowls on the outside. It became more or less SOP for me to drop the bowls after the motor had cooled down to check for water collecting in the bottom. From time to time there was a small bead of it in there.
High humidity also acts to increase the effective density altitude since water vapour is less dense than air so, as Dana said, everything will go rich in those conditions.
If you're already rich at idle, it'll be aggravated pretty good as the humidity rises.
You might also make sure your idle jets are clear. Those are the first parts to plug up on the 2-stroke bings, especially if you're running premix. Being unable to get a lean enough idle is the typical symptom of this. You even see this from time to time on the 912 bings, as one of our locals found out on his 912ULS here a few weeks ago.....
LS
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LS
Titan II SS |
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zeprep251(at)aol.com
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| Posted: Wed Jun 03, 2009 6:43 am Post subject: strange sputtering |
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Cristal,
When you evaporate fuel at the discharge nozzle,it is possible to get a temperature drop of 30 degrees or more,and under high humidity conditions have some ice form on the inside of the carb body affecting fuel discharge at low speed.It,s less likely with the Bing 54 than on the 64CV Bings on the 912,s and Jabiru's because they also have a throttle plate downwind of the discharge nozzle which ice forms on readily.On my 64CV I use an electrically powered heater unit that mounts with 2 screws to the boss at the throttle shaft and it heats the shaft area of the carb body effectively. Got it from the Jabiru dealer.I doubt if you will have enough trouble with icing to warrant that much effort.Just watch for those days of high humidity and temps when a 30 degree drop could put you in that freezing range, and make your throttle movements carefully.
G.Aman MK3C 2200Jabiru
--
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JetPilot
Joined: 10 Jan 2006
Posts: 1246
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| Posted: Wed Jun 03, 2009 8:43 am Post subject: Re: strange sputtering |
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I don't think Carb icing is a possibility in Crystal's case. The outside temp was probably 85 degrees or maybe even hotter. Even with a 30 degree temperature drop in the carburetor, that is not even close to forming ice. There is a lot of humidity, and the carbs will sweat due to them being much cooler than the surrounding air flowing over them, but it ice just is not going to form in a carburetor on an 85 degree day.
Better not to get distracted with something that was not the problem, and look for the real culprit to the rough running engine.
Mike
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"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Wed Jun 03, 2009 8:51 am Post subject: Re: strange sputtering |
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Carb ice can form at 85F OAT in high humidity. See graph at following link.
http://www.ez.org/carb_ice.htm
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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dalewhelan
Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills
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| Posted: Wed Jun 03, 2009 6:12 pm Post subject: Re: strange sputtering |
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One person posted that it was possible the pilot jet was plugged. I think he meant to say this would cause a lean condition, as plugging up a fuel jet reduces fuel delivery. When they are lean throttle response is poor, just like when the motor is too cold.
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Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept |
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