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912UL rough at around 4000

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parahawk

Joined: 10 Jul 2006
Posts: 21
Location: Washington State

Posted: Sat Nov 11, 2006 7:21 pm Post subject: 912UL rough at around 4000

My 912UL with 185 hrs. runs rough at the range between 3900 and 4100 rpm. Above and below rpm's as well as idle are OK.  

It has always done it since I got the plane with 150 hrs. TT.



Any suggestions ??

Thanks

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Flying is the highest form of life on earth.

lostpilot28

Joined: 26 Jul 2006
Posts: 7
Location: Southern California

Posted: Sat Nov 11, 2006 8:55 pm Post subject: Re: 912UL rough at around 4000

Mine runs rough between 4000 and 4200 RPMs...if you find out what causes this, let me know.  I have 288 hours on mine.  



Also, I've noticed that lately (maybe because it's getting colder here in the North-West) that if I quickly advance the throttle from a mid-range setting that my engine sputters for about 2 seconds before it picks up.



I've checked the float levels and the diaphragms in the Bing carbs....all normal.  If anyone has a suggestion about the hesitation, please let me know.  Thanks.



Regards,

Sonny W.

Horizonspace(at)aol.com
Guest

Posted: Sat Nov 11, 2006 9:43 pm Post subject: 912UL rough at around 4000

In a message dated 11/11/2006 10:57:09 P.M. Central Standard Time,  lostpilot28(at)yahoo.com writes:

  	  Quote: 	
		  -->    RotaxEngines-List message posted by: "lostpilot28"    <lostpilot28(at)yahoo.com>



Mine runs rough between 4000 and 4200    RPMs...if you find out what causes this, let me know.  I have 288 hours    on mine.  



Also, I've noticed that lately (maybe because it's    getting colder here in the North-West) that if I quickly advance the throttle    from a mid-range setting that my engine sputters for about 2 seconds before it    picks up.



I've checked the float levels and the diaphragms in the Bing    carbs....all normal.  If anyone has a suggestion about the hesitation,    please let me know.  Thanks.



Regards,

Sonny  W. 	


 

 Check the jet needle settings.  These govern midrange RPM  mixture.  Our 914 was incorrectly set from the factory.  Perform mag  drop per the manual.  Check spark plug boots for corrosion.  Good  luck!

  [quote][b]

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Sun Nov 12, 2006 2:53 am Post subject: 912UL rough at around 4000

Oddly the same thing has happened recently to people on the kitfox list. I 

do not have a 912 but I am led to understand that lowering the clip on the 

jet needle by one notch ( raising the needle a little) will make the mid 

range slightly richer and cure this problem. Again, I have never touched a 

912 and am simply passing on what I read. Hope it helps.

lostpilot28

Joined: 26 Jul 2006
Posts: 7
Location: Southern California

Posted: Sun Nov 12, 2006 8:21 am Post subject: Re: 912UL rough at around 4000

Hey guys,

Thanks...this sounds like what I need to do.  How exactly do you adjust the Needle Jets, though?  I'm no carb guru, but I thought the only way to adjust them was to replace them with shorter/longer jets.



If you CAN adjust them (by a turn of a screwdriver, per se), how do you know what the new setting is or will do?  



Much thanks!



Sonny W.

Thom Riddle

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

Posted: Mon Nov 13, 2006 5:55 am Post subject: 912UL rough at around 4000

Before you go messing with the Bing carbs I would spend $10 on this 

Bing Manual and learn all about all the various circuits, how to 

synchronize them etc.



http://www.bingcarburetor.com/manual.html



Thom in Buffalo

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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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lostpilot28

Joined: 26 Jul 2006
Posts: 7
Location: Southern California

Posted: Fri Nov 17, 2006 4:38 pm Post subject: Re: 912UL rough at around 4000

Problem resolved.  I spoke with a Bing guy earlier in the week who said the jets were worn and it was running too rich.  He was wrong.



Today I pulled the plugs & all were white except the #1 cylinder, which is always black for some reason.  Majority rules - it's running lean.  I called Bing back from the airport and a different guy said a good way to test if it's too lean is to actuate the choke when it's running rough.  If it's too lean, this will richen the mixture and smooth it out.  He was right. I tried this while flying and it jumped up about 150 RPMs and smoothed out.



I landed, moved the clip on the needle from the #2 position to the richer #3 position and went flying again.  Smooth as silk.  Thanks to those of you that provided feedback...your help was greatly appreciated!



Regards,

Sonny W.

Thom Riddle

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

Posted: Sat Nov 18, 2006 5:54 am Post subject: 912UL rough at around 4000

lostpilot28,



...Today I pulled the plugs & all were white except the #1 cylinder, 

which is always

      black for some reason.....



I experienced the sooty #1 plugs earlier this year on our 912UL but the 

rest were nice tan color and the carbs did not need to be leaned out, 

as yours did, although I took them both apart, checked the jets and 

needle numbers and the needle settings, which were all correct. The 

engine was not running rough either.



It took me quite a while to discover the problem but I finally did. One 

of the small gauge white ignition circuit wires was broken. I found it 

by visually inspecting every inch of the exposed wires. I don't recall 

which one but it apparently was affecting this cylinder only. Once I 

found and repaired the broken wire the plugs no longer turned black and 

were very close to the same rich/lean color as the rest.



Good luck.



Thom in Buffalo

_________________
Thom Riddle
Buffalo, NY (9G0)

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

lostpilot28

Joined: 26 Jul 2006
Posts: 7
Location: Southern California

Posted: Sat Nov 18, 2006 7:40 am Post subject: Re: 912UL rough at around 4000

Hi Thom,

Thanks for the tip! I'm going to go check out my wiring today.  It sounds like the same thing that's happening to me...can you tell me the location of the broken wire?  I'll start there just in case I get lucky.  Thanks again.



Regards,

Sonny

Thom Riddle

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

Posted: Sun Nov 19, 2006 5:06 am Post subject: 912UL rough at around 4000

Sonny,



Every 912 installation is different. Ours is in an Allegro 2000 and the 

broken white wire was on the right side tie-wrapped to the engine 

mount. I know one end lead to the ignition module on top of the engine 

but don't recall where the other end went. If I had built the airplane 

I'm sure I could tell you more.



Good luck.



Thom

_________________
Thom Riddle
Buffalo, NY (9G0)

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

Roger Lee

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

Posted: Sun Dec 10, 2006 7:32 am Post subject: Re: 912UL rough at around 4000

Hi Guys,



This can be typical if your carbs are out of sync. do the manual sync and then the vacumm guage sync. It should go away.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
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