Bing 54 jet size adjustments for altitude

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Jay Dub

Active Member
Joined
Dec 17, 2019
Messages
31
Location
SE WY
I have plenty of experience dialing in motorcycle (2 & 4 cycle) and chainsaw carbs.

I have a 447 Rotax with the single factory Bing 54 carb that I just put new seals and gaskets in that I will be installing on a Kolb Firestar II. The Bing is stock with the 165 main. I live at 4600'msl so I need to lean it some and I've looked at charts such as this bing chart and I'm thinking I'll use the sizing factor of .96 (4500', 59F) as I will be a little rich in the heat of summer but good enough even at 45-50F. I doubt I'll fly the Kolb in colder weather than that.

165 x .96= 158.4. I can buy a 158 main jet, so a perfect starting point. That doesn't help me with the sizing of the idler jet or needle jet. The main jet controls the max fuel at WOT. The needle controls fuel in the midrange (has some adjustment via clip). The idler of course deals with idle and transition to mid-range. Do the needle or idler jet typically get changed to compensate for altitude with the rotax 2 strokes? It seems they would be but perhaps with the clip I can drop it enough to get it right in the mid range and the idle air screw might let me dial in the idle mixture. I haven't dialed in a Bing 54 on a Rotax before so asking if anyone has some experience with them.

I will be using a dual EGT gauge when I get ready to do the break-in.

Any good advice is appreciated.
Jay
 

Jay Dub

Active Member
Joined
Dec 17, 2019
Messages
31
Location
SE WY
I found on leading edge airfoils website a pdf for tuning the Bings and it says "To adjust the carburetor, in general, a different main jet size is sufficient. Only in very particular cases does a different needle jet and/or different idle jet have to be installed." This is good as I only need to buy the main jet.

I didn't realize Green Sky Adventures was still around. I had heard Jerry Olenik had passed away. Jerry always treated me well and did my Rotax rebuilds in the early 90's as we lived just a few miles away in the same County in NE, OH.
 

Tim Newport

Member
Joined
Oct 3, 2019
Messages
9
I have plenty of experience dialing in motorcycle (2 & 4 cycle) and chainsaw carbs.

I have a 447 Rotax with the single factory Bing 54 carb that I just put new seals and gaskets in that I will be installing on a Kolb Firestar II. The Bing is stock with the 165 main. I live at 4600'msl so I need to lean it some and I've looked at charts such as this bing chart and I'm thinking I'll use the sizing factor of .96 (4500', 59F) as I will be a little rich in the heat of summer but good enough even at 45-50F. I doubt I'll fly the Kolb in colder weather than that.

165 x .96= 158.4. I can buy a 158 main jet, so a perfect starting point. That doesn't help me with the sizing of the idler jet or needle jet. The main jet controls the max fuel at WOT. The needle controls fuel in the midrange (has some adjustment via clip). The idler of course deals with idle and transition to mid-range. Do the needle or idler jet typically get changed to compensate for altitude with the rotax 2 strokes? It seems they would be but perhaps with the clip I can drop it enough to get it right in the mid range and the idle air screw might let me dial in the idle mixture. I haven't dialed in a Bing 54 on a Rotax before so asking if anyone has some experience with them.

I will be using a dual EGT gauge when I get ready to do the break-in.

Any good advice is appreciated.
Jay
[email protected]
I have no experience with a smart carb. But it sure does make a whole hell of a lot of sense. Automatically adjust for altitude and temperature. . No more messing with jets.
 
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