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912UL rough at around 4000

 
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parahawk



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

PostPosted: Sat Nov 11, 2006 7:21 pm    Post subject: 912UL rough at around 4000 Reply with quote

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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lostpilot28



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

PostPosted: Sat Nov 11, 2006 8:55 pm    Post subject: Re: 912UL rough at around 4000 Reply with quote

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.


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PostPosted: Sat Nov 11, 2006 9:43 pm    Post subject: 912UL rough at around 4000 Reply with quote

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]


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occom



Joined: 26 Aug 2006
Posts: 404

PostPosted: Sun Nov 12, 2006 2:53 am    Post subject: 912UL rough at around 4000 Reply with quote

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.


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lostpilot28



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

PostPosted: Sun Nov 12, 2006 8:21 am    Post subject: Re: 912UL rough at around 4000 Reply with quote

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.


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Thom Riddle



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

PostPosted: Mon Nov 13, 2006 5:55 am    Post subject: 912UL rough at around 4000 Reply with quote

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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lostpilot28



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

PostPosted: Fri Nov 17, 2006 4:38 pm    Post subject: Re: 912UL rough at around 4000 Reply with quote

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.


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Thom Riddle



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

PostPosted: Sat Nov 18, 2006 5:54 am    Post subject: 912UL rough at around 4000 Reply with quote

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


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Buffalo, NY (9G0)



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lostpilot28



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

PostPosted: Sat Nov 18, 2006 7:40 am    Post subject: Re: 912UL rough at around 4000 Reply with quote

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


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Thom Riddle



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

PostPosted: Sun Nov 19, 2006 5:06 am    Post subject: 912UL rough at around 4000 Reply with quote

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


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Thom Riddle
Buffalo, NY (9G0)



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Roger Lee



Joined: 10 Jan 2006
Posts: 1461
Location: Tucson, Az.

PostPosted: Sun Dec 10, 2006 7:32 am    Post subject: Re: 912UL rough at around 4000 Reply with quote

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.


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