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cristalclear13
Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia
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 Posted: Sun Oct 12, 2008 6:31 pm Post subject: Bing carb tuning |
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I read this on the ultralightnews.com website and am wondering how someone would safely adjust the air screw while the engine is running since the air screw faces the propeller?
<quote>This air screw changes the air/fuel mixture by changing the ratio of air to the idle jet circuit. Turning the screw out with lean the mixture while turning it in richens it.
After referring to the jet chart you have a position to start from. With the engine warmed up and idling and the screw set to factory specs turn the screw out very slowly - the engine should start to pick up rpm as you lean the mixture out. If nothing happens the low speed jet is probably plugged, or the small atomizer hole located in the throat of the carb on the engine side is blocked.
Once you have the engine idling at its highest and leanest setting using the air screw turn the screw back in 1/8 of a turn which will richen it up just enough for the best performance.
Note it is usually necessary to do this three or four times a year, do to the difference in air that you get in spring/summer/fall/winter.</quote>
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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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cristalclear13
Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia
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| Posted: Sat Oct 18, 2008 12:14 pm Post subject: Re: Bing carb tuning |
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| cristalclear13 wrote: | I read this on the ultralightnews.com website and am wondering how someone would safely adjust the air screw while the engine is running since the air screw faces the propeller?
<quote>This air screw changes the air/fuel mixture by changing the ratio of air to the idle jet circuit. Turning the screw out with lean the mixture while turning it in richens it.
After referring to the jet chart you have a position to start from. With the engine warmed up and idling and the screw set to factory specs turn the screw out very slowly - the engine should start to pick up rpm as you lean the mixture out. If nothing happens the low speed jet is probably plugged, or the small atomizer hole located in the throat of the carb on the engine side is blocked.
Once you have the engine idling at its highest and leanest setting using the air screw turn the screw back in 1/8 of a turn which will richen it up just enough for the best performance.
Note it is usually necessary to do this three or four times a year, do to the difference in air that you get in spring/summer/fall/winter.</quote> |
Ok, maybe that was a stupid question?
How about this...do you adjust the air screw every season as suggested?
If so, what's your procedure?
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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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Tom Jones
Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA
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| Posted: Mon Oct 20, 2008 6:50 am Post subject: Re: Bing carb tuning |
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| Quote: | | am wondering how someone would safely adjust the air screw while the engine is running since the air screw faces the propeller? |
Crystal, I wonder the same thing. When I first set up my 503 I read those instructions then went out and looked at the close proximity of the prop to the front carb air screw and said to myself, "Self, no way!"
I tried turning the screws a slight amount with the engine off, then starting it up to check the rpms and smoothness. I ended up with the screws right back where the instructions recommended for the initial setting.
I have not found that I need to change carb jets, or adjustments nor prop pitch with the seasons on this engine. My 503 is the DCDI model. It runs like a sewing machine year round.
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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Tue Oct 21, 2008 2:04 pm Post subject: Bing carb tuning |
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The airscrews only come into play when the engine is idling... As long as you don’t idle your engine for extended periods except for a five minute warm up I wouldn’t worry about it... just use the factory defaults. The engine is designed to run a bit rich at the idle so extended periods of idling may cause your plugs to foul. At full throttle engine mix can be adjusted by loading the engine ( richer ) and changing the main jet in the carbs. Several people will also change the height of the jet itself with the seasons to give a bit richer mix at cruise throttle during cold months when the air is more dense.
About the five minute warm up. I actually keep a stop watch in the plane for the warm up. Two minutes at a 2000 rpm idle. Two minutes at 3000rpm by this time the instruments should be stabilized and an additional minute at 3500 rpm. Once that is done I will do my mag and throttle tests. This procedure was recommended to me by a Rotax repair centre.
A bonus to having the stopwatch left in the plane is I then have a watch and timer for my flight. I start the flight time when I firewall the throttle and end it when the plane has come off step (floats). I use hobbs time for engine maintenance.
Noel
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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