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Bing Type 64 Carb. Idle Mixture Setting

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hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Wed Mar 02, 2011 7:44 pm Post subject: Bing Type 64 Carb. Idle Mixture Setting

In reading the Pro Carb Shop Manual for the Bing Type 64 Carbs used on the  Rotax 912 UL engine, on page 16 under section â€œIdle Mix Settingâ€, the procedure  is written as if there is only one carb. Of course on the Rotax 912 UL (as well  as 912 ULS and other 912s) there are two carbs. I assume one would follow this  procedure for one of the carbs, and do the same for the other carb. Would   you have to go back to the first carb and re-adjust after the second carb was  adjusted? Anyone have any experience doing this?

  

 Hugh G.  McKay III

 Allegro  2000

 Rotax 912  UL

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Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Thu Mar 03, 2011 4:50 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hugh,



If you are happy with the balance/synch of the two carbs but not happy with the idle mixture, then any adjustments you make to one idle mixture should be done to both. Once you get the two idle mixtures to where you are happy, then you should check the synch again. It should not change much, if any, as long as you make the idle mixture adjustments equal on both carbs.



If I may ask, what triggered the need to make idle mixture adjustments?

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Thu Mar 03, 2011 5:47 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Thom,

Some time ago I had a rough engine problem which was finally traced to a 

broken wire at one of the modules. In the course of trying a number of 

things to find the problem, one of the things I did was to re-set the idle 

mixture. I closed the idle mixture screw on both carbs and then backed them 

out the 1.5 turns per Rotax. Unfortunately I did not index the original 

position of the screws so I don't know exactly where they were set by the 

factory (i.e. 1.5, 1.8 ,or say 2.0 etc). Anyway, my plugs have a black 

velvet coating on them every time I change them, and the inside of my 

exhaust is black and sooty. My reading has reading on this has indicated 

that my idle mix setting is too rich, so I am going to try and readjust them 

per the Pro Carb Shop procedure. Any suggestions?



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 03, 2011 6:09 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hi Hugh,



The factory setting is 1.5 turns. You can tweak these some and clean up the idle mixture. It will not effect any thing above idle. The black dry velvet can be normal and only happens at idle. When you are cruising then this does not happen. Because of the way the air intakes are setup you can have a slight difference between sides on the mixture. You actually can just tweak one side if need be and it won't hurt any thing. The black velvet won't hurt a thing and you shouldn't be at idle for long periods anyway. Most of the time your engine is well above that so it isn't a factor so the other option is to just leave it alone. My plane will have it sometimes and other times it doesn't, plus it may move from one plug to another. It is a small item and not one that I would worry too much about.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Thu Mar 03, 2011 6:13 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hugh,



Just make small adjustments, no more than 1/8th turn (45 degrees) at a time, on both carbs, from the original 1.5 turn starting point. Run the engine and check again. 



Keep in mind that these affect only the mixture at idle speed or slightly above idle speed and that at idle, they must be fairly rich to come off idle smoothly without stuttering or balking. The plugs will show black sooty appearance after extended idle periods even when it is adjusted perfectly, because it must be somewhat rich at idle. The color inside the exhaust tip reflects more accurately the normal cruise speed mixture, and should be less black and more gray in color. If you run the engine under less load than recommended (too little prop pitch or too slow rpm) then the exhaust color may be black. If you have EGTs installed, the normal cruise temps should be approximately 1,470F with a max of 1,560F.



In my experience with prop pitched properly, the 912UL will have the proper EGT readings above 4800 rpm or so with gradual drop off below that speed range.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Thu Mar 03, 2011 6:56 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Thom/Roger,

Thank you for your counsel and advice. My exhaust is certainly not grey. It 

is black and sooty! My prop pitch is is 15 degrees which gives me 5100 

Static rpm. The following three tests were run to set my prop pitch:



First Test     Pitch 17.5 degrees    rpm 4600

Second Test    Pitch 16.5 degrees    rpm 4900

Third Test    Pitch 15 degrees        rpm 5100



I have been happy with the pitch at 15 degrees. When I cruise I keep the 

engine rpm between 5200 to 5400 rpm. Under this condition (cruise) I am not 

at WOT. On take off (WOT), my rpm is around 5100. I still think I am too 

rich because of the black sooty exhaust.



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 03, 2011 8:00 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hi Hugh,



With the rpm numbers you give sounds like you are little under propped. What do you get at WOT flat and level? It sounds like you may be close to 5700 WOT? It won't hurt anything, but you'll loose a little cruise speed and fuel economy.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Thu Mar 03, 2011 8:39 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Roger,

I never fly WOT while cruising. I will fly today and open her wide open and 

check the rpm. I will let you know.



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Wed Mar 09, 2011 6:27 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Roger,



I finally got around to flying yesterday. I flew the Allegro 2000 at WOT in 

level flight. At WOT in level flight my speed was around 120 mph and 

climbing. My rpms were very close to 5800, and if I would have continued at 

WOT I am sure the rpms would have exceeded 5800, and the speed would have 

exceeded 120 mph. However, I did not let the engine get to 5800. I backed 

off the throttle to prevent reaching 5800. With WOT at take off and climb 

out at 68 to 70 mph the rpm is at 5200.

Comments??



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Wed Mar 09, 2011 1:57 pm Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hi Hugh,



Way under propped for a ground adjustable for your type of aircraft. If it does get to 5800+ rpm you may even be loosing climb. I would try and add more pitch of at least 2 degrees, you may need a more like 2.5 degrees more pitch. Try and get it around 5500-5550 WOT flat and level and then report back. It will have better all around performance including fuel economy without sacrificing one characteristic over the another. I have a friend on another forum with an Allegro and we set his up for 5500 area and he loves it.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Wed Mar 09, 2011 2:20 pm Post subject: Bing Type 64 Carb. Idle Mixture Setting

Roger,



I assume you mean 5500 - 5550 rpm (static). Correct?



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Wed Mar 09, 2011 6:16 pm Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hi Hugh,



5500-5550 WOT while you are flying flat and level at your average cruise altitude. So add about 2.5 degrees pitch back into your prop. Then go fly. Go WOT flat and Level for 30-60 seconds and see where it tops out at for rpm. If you need to tweak it after that then it will be a very small adjustment, but 2.5 added ought to be close.

 You have the prop set in the general area so we don't really care about the static any more. Static changes for all props and I only use static for the the very first run on a prop that I have no experience with. Static is just to get in the ballpark. WOT while flying is the only real way to get an accurate WOT rpm.



Trust me, you'll like it.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Thu Mar 10, 2011 5:04 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Hugh,

Roger is correct. I had our Allegro set up for 5500 WOT straight and level in-flight. On the Allegro 2000 that turned out to be about 4800-4900 static rpm on the ground. So for your first adjustment, add some pitch, at least one full degree, tie down the airplane and do a full throttle static rpm test after the engine is warmed up properly. 



If the ground static is over 4900 rpm, add a bit more pitch to get it in the 4800-4900 rpm range and then go fly it and check the WOT S&L rpm. 5500 rpm +/- 50 rpm is your goal. Your climb performance won't be quite as good as it is now but all around performance and economy will be much better and your spark plugs will not be so black, except after prolonged periods of idle.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Thu Mar 10, 2011 6:24 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Roger, Thom:



OK, I've got it. I will start by changing the pitch from 15 degrees(where it 

is now), to 16.5 degrees and try it. I will probably miss the climb-out 

performance I am now getting, but you can't "have your cake and eat it to".



Hugh G. McKay III, P.E.

Senior Consultant

Worldwide Engineering Inc.

4090 North NC Hwy. 16

Denver, NC 28037



Ph. 704-661-8271

Fax 704-483-5466

email hgmckay(at)bellsouth.net

http://www.wwegeo.com

--

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Thu Mar 10, 2011 6:24 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

>You have the prop set in the general area so we don't really care about  the static

      any more. Static changes for all  props and I only use static for the the

      very  first run on a prop that I have no experience with. Static is just to  get

      in the ballpark. WOT while flying is the  only real way to get an accurate WOT

       rpm.<

  

  

 Keep in mind Roger that Rotax has a recommended static rpm  limit of 5200 rpm(WOT) or above ( in order to reduce the possibility  of engine case cracking). This was spelled out in a service bulletin.

                       

                                                 Dick Maddux

                                                 Milton,Fl 

 [quote][b]

ollie6a(at)embarqmail.com
Guest

Posted: Thu Mar 10, 2011 7:24 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

How much time do you spend at WOT static? I get 5250 rpm on climb out

at 70-80 mph with my S7S which gives me 5500-5600 rpm WOT level flight

and about 120-125 mph. Not bad for a cub type airplane. I cruise at

5200 rpm and indicate 108-110 mph as backed up by gps.

Ollie

On Thu, Mar 10, 2011 at 9:15 AM,  <Catz631(at)aol.com> wrote:

 	  Quote: 	
		  >You have the prop set in the general area so we don't really care about the

> static

 Â Â Â Â Â  any more. Static changes for all props and I only use static for the

 the

 Â Â Â Â Â  very first run on a prop that I have no experience with. Static is

 just to get

 Â Â Â Â Â  in the ballpark. WOT while flying is the only real way to get an

 accurate WOT

 Â Â Â Â Â  rpm.<

 Keep in mind Roger that Rotax has a recommendedÂ static rpm limitÂ of 5200

 rpm(WOT) or aboveÂ ( in order to reduce the possibility of engine case

 cracking). This was spelled out in a service bulletin.

 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Dick Maddux

 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Milton,Fl

-- 

 	  Quote: 	
		  From Central Florida,

Â Ollie

VIXEN

Joined: 23 Nov 2009
Posts: 35

Posted: Thu Mar 10, 2011 7:44 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

Hello Hugh



Not sure about the Allegro, but the installation of an IFA prop solved all these issues on my Kitfox Vixen. I just have the 912UL (80HP) and it has made a "whole new aircraft" out of it.

You may not be able to do this as a sport aircraft, not sure.

 

Don



On Thu, Mar 10, 2011 at 6:17 AM, Hugh McKay <hgmckay(at)bellsouth.net (hgmckay(at)bellsouth.net)> wrote:

[quote] --> RotaxEngines-List message posted by: "Hugh McKay" <hgmckay(at)bellsouth.net (hgmckay(at)bellsouth.net)>

 



 Roger, Thom:

 

 OK, I've got it. I will start by changing the pitch from 15 degrees(where it is now), to 16.5 degrees and try it. I will probably miss the climb-out performance I am now getting, but you can't "have your cake and eat it to". 

 

 Hugh G. McKay III, P.E.

 Senior Consultant

 Worldwide Engineering Inc.

 4090 North NC Hwy. 16

 Denver, NC 28037

 

 Ph. 704-661-8271

 Fax 704-483-5466

 email hgmckay(at)bellsouth.net (hgmckay(at)bellsouth.net)

 http://www.wwegeo.com



 --

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Fri Mar 11, 2011 4:33 am Post subject: Bing Type 64 Carb. Idle Mixture Setting

> How much time do you spend at WOT static? I get 5250 rpm on climb  out

      at 70-80 mph with my S7S which gives me  5500-5600 rpm WOT level flight

      and about  120-125 mph.<

  

 Ollie,

  I am getting the same rpm in my Kitfox on take off (5250) as you.  Granted you don't spend much time at static during the take off roll but Rotax  still wants you to have 5200 or above. I asked why at a recent  Rotax refresher course.  The instructor told me that it was due to  prop induced overload and case cracking they found on the earlier  engines (mine is one) The 912 now has a heavier/stronger case. I don't remember  the date when the switch was made. I have the service bulletin spelling out the  5200 limit but don't remember the number. ( one of a bunch !) I can get it  if you want.

                                          Dick Maddux

                                           Milton,Fl

 [quote][b]

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Fri Mar 11, 2011 6:28 am Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

On take off rpm you can get higher rpms by a shallower take off and less or no flaps. Their 5200 rpm on take off will usually get you close to 5800 rpm WOT flat and level. Most of us try and shoot for around 5000 on take off, but this is a little lower than the SB. Rotax was really trying hard to get people away from the 4500-4800 rpm take offs and WOT settings at cruise of less than 5500 (i.e 5000-5300). Having a prop set to only get 5300 or less WOT flat and level is stress on the crank case and other parts. If you can see 5500-5600 WOT flat and level then you should be good. You also should not be using less than 5000 for extended cruise settings. A good place to be is to have the prop set to get engine rpm of 5500-5600 WOT flat and level and cruise between 5000-5300 rpm. Better on the higher rpms if you use 100LL. These setting should give you the best all around performance for a fixed pitch prop. If you have an in air adjustable then you can dial in what works well during the different stages of your flight.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Rich L

Joined: 23 Feb 2008
Posts: 63
Location: North Idaho

Posted: Mon Mar 14, 2011 5:42 pm Post subject: Re: Bing Type 64 Carb. Idle Mixture Setting

Here are some numbers I got after reading this topic last week.

Started off with about 5150 on lift off and 5820 WOT.

I could put the nose to the sky and climb forever (well almost).



After three adjustment tries, I got it to 4850 on lift off and 5650 WOT.



I lift off in about the same distance but keep the nose down to almost level flight.  100 feet after liftoff I am at 5000 and 100 feet farther, I am at 5200.  Then I can pull it back to a good climb out.



I have gained more than 5 mph at 5200 cruise so I will leave the pitch here for awhile.

I have the Kiev Prop.

_________________
Rich Little
N812RL S-7 912ULS
North Idaho
Kiev Prop

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