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912 rough running below 3000 rpm
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pjeffers(at)talktalk.net
Guest

Posted: Wed Jun 03, 2015 6:35 am Post subject: 912 rough running below 3000 rpm

Hi Roger,

When I have done this job in the past I used a special Rotax tool for the

correct set up.

It was drawn to my attention that the dimension you refer to varies with

engine type ie 912ul 912uls and 914. Your clarification on this may be

appreciated by many or just me.

Pete



--

Roger Lee

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

Posted: Wed Jun 03, 2015 7:31 am Post subject: Re: 912 rough running below 3000 rpm

Rotax does have a special measurement tool the slips over the main jet nipple area. I was doing this before that tool came out so just stuck with the mm ruler and saved about $35. 



Most don't want to spend the money on what many would consider a one time use part, but either way works and gets the job done.

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

pjeffers(at)talktalk.net
Guest

Posted: Wed Jun 03, 2015 7:53 am Post subject: 912 rough running below 3000 rpm

Roger,

My query was more about the dimension of 10.5 mm.  I was told (and the tool

indicates) that different figures apply to the 912, 912s and 914 engines. I

am not too sure how critical this is but the dimensions on the tool are

quite different.

Pete



--

vernon11

Joined: 03 Aug 2010
Posts: 14

Posted: Wed Jun 03, 2015 9:22 am Post subject: 912 rough running below 3000 rpm

Pete,

      If that is the case, I would be very interested.

Vernon.



--------------------------------------------------

From: "Peter Jeffers" <pjeffers(at)talktalk.net>

Sent: Wednesday, June 03, 2015 4:34 PM

To: <rotaxengines-list(at)matronics.com>

Subject: RE: Re: 912 rough running below 3000 rpm



[quote] 

 <pjeffers(at)talktalk.net>



 Hi Roger,

 When I have done this job in the past I used a special Rotax tool for the

 correct set up.

 It was drawn to my attention that the dimension you refer to varies with

 engine type ie 912ul 912uls and 914. Your clarification on this may be

 appreciated by many or just me.

 Pete



 --

pjeffers(at)talktalk.net
Guest

Posted: Wed Jun 03, 2015 10:51 am Post subject: 912 rough running below 3000 rpm

Hi Vernon,

Some years ago I renewed all the maintainable bits of my carbs on a 912ul.

This included the brass pivot arm . At the time I rather naively assumed

that it was just a replacement item and fitted it as supplied in a Rotax

kit. I flew the aircraft and had no problem at all until I throttled back at

top of climb at which time the engine ran very rough. So rough that I

declared an emergency. 

The simple fix was to correctly adjust the float levels in both carbs using

the Rotax tool.The tool has steps in it for the different 900 series

engines. I have absolutely no problem doing this with a tape measure as

Roger has described, but according to which engine you are working on

depends what dimension you should be working to.  I look forward to Roger's

reply as he is the oracle on these matters.

Pete



--

vernon11

Joined: 03 Aug 2010
Posts: 14

Posted: Wed Jun 03, 2015 11:12 am Post subject: 912 rough running below 3000 rpm

Yes Pete,

          I will be looking forward to Rogers reply as well. Small things 

like that, can make a big difference.

Vernon



--------------------------------------------------

From: "Peter Jeffers" <pjeffers(at)talktalk.net>

Sent: Wednesday, June 03, 2015 8:35 PM

To: <rotaxengines-list(at)matronics.com>

Subject: RE: Re: 912 rough running below 3000 rpm



[quote] 

 <pjeffers(at)talktalk.net>



 Hi Vernon,

 Some years ago I renewed all the maintainable bits of my carbs on a 912ul.

 This included the brass pivot arm . At the time I rather naively assumed

 that it was just a replacement item and fitted it as supplied in a Rotax

 kit. I flew the aircraft and had no problem at all until I throttled back 

 at

 top of climb at which time the engine ran very rough. So rough that I

 declared an emergency.

 The simple fix was to correctly adjust the float levels in both carbs 

 using

 the Rotax tool.The tool has steps in it for the different 900 series

 engines. I have absolutely no problem doing this with a tape measure as

 Roger has described, but according to which engine you are working on

 depends what dimension you should be working to.  I look forward to 

 Roger's

 reply as he is the oracle on these matters.

 Pete



 --

rv10pro(at)gmail.com
Guest

Posted: Wed Jun 03, 2015 11:52 am Post subject: 912 rough running below 3000 rpm

This is an excellent example of what is great with Matronics.  I too look forward to Roger's response.  Although rather than call him an "Oracle",  google answers  "A response which is typically one that is ambiguous or obscure".



 I would prefer you use the term Pontiff as in officiating such as at mass.  I hold Rotax as the ultimate authority and this is no time for ambiguous or obscure dogmatic answers.  I like your method mentioned above.  I love the 912iS with Fadec.

John Cox.

On Wed, Jun 3, 2015 at 12:11 PM, vernon mitchell <vernon11(at)xsinet.co.za (vernon11(at)xsinet.co.za)> wrote:

[quote]--> RotaxEngines-List message posted by: "vernon mitchell" <vernon11(at)xsinet.co.za (vernon11(at)xsinet.co.za)>

 

 Yes Pete,

          I will be looking forward to Rogers reply as well. Small things like that, can make a big difference.

 Vernon

 

 --------------------------------------------------

 From: "Peter Jeffers" <pjeffers(at)talktalk.net (pjeffers(at)talktalk.net)>

 Sent: Wednesday, June 03, 2015 8:35 PM

 To: <rotaxengines-list(at)matronics.com (rotaxengines-list(at)matronics.com)>

 Subject: RE: Re: 912 rough running below 3000 rpm

 

 [quote] --> RotaxEngines-List message posted by: "Peter Jeffers" <pjeffers(at)talktalk.net (pjeffers(at)talktalk.net)>

 

 Hi Vernon,

 Some years ago I renewed all the maintainable bits of my carbs on a 912ul.

 This included the brass pivot arm . At the time I rather naively assumed

 that it was just a replacement item and fitted it as supplied in a Rotax

 kit. I flew the aircraft and had no problem at all until I throttled back at

 top of climb at which time the engine ran very rough. So rough that I

 declared an emergency.

 The simple fix was to correctly adjust the float levels in both carbs using

 the Rotax tool.The tool has steps in it for the different 900 series

 engines. I have absolutely no problem doing this with a tape measure as

 Roger has described, but according to which engine you are working on

 depends what dimension you should be working to.  I look forward to Roger's

 reply as he is the oracle on these matters.

 Pete

 

 --

flynn elliott

Joined: 23 Jun 2007
Posts: 20
Location: SOUTH AFRICA

Posted: Wed Jun 03, 2015 12:48 pm Post subject: 912 rough running below 3000 rpm

A glimmer of hope, pulled the jets yet again and this time also the mixture

needles and gave them a clean and a light blast of air, along with the brass

down pipe attached to the carb body, reassembled and fired up, smooth as

silk at idle and throttle progression for around fifteen seconds then back

to lumpy running. Think I dislodged a tiny piece of something which may have

got pushed back with the fuel flow. I get the impression the culprit is

sitting in the carb body, will now have to take the carbs off for a strip

down be it that maybe only one carb is causing the problems.

Oh ,and float levels are spot on.

Flynn



--

Roger Lee

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

Posted: Wed Jun 03, 2015 4:31 pm Post subject: Re: 912 rough running below 3000 rpm

The 912UL and ULS are the same measurements. They are the same carbs just different jetting.



When the carbs come off you must flush through every orifice and jet in the bowl and carb body and leave no stone unturned. It only takes a very tiny piece of debris to cause this rough running. Your symptoms do sound like you move a piece of debris, but after it runs it moves again.

I absolutely know you don't want to hear this, but I think you missed something on the cleaning. Every little hole and crevice needs to be flushed then blown out with air. Blow the air in more than one direction where possible. I have seen a few owners have difficulty here because they left one stone unturned.



Thanks for the vote of confidence, but no "Oracle" here just an owner like everyone else and happy to pass on what I learn in all the Rotax schools and what I have been able to see over the years. matter of fact I just spent all  last week back at Rotax for another school. I'm always happy to help if I can. People have certainly helped me over the years.

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

pjeffers(at)talktalk.net
Guest

Posted: Thu Jun 04, 2015 1:35 am Post subject: 912 rough running below 3000 rpm

Hi Roger,

I have now had the chance to read up on some old documents that I have and

can now confirm that the setup dimensions for the floats on the 912l and

912s engines are both the same ie 10.5 mm but the 914 is quite different.

Pete

ps I cannot quite relate the dimensions on the Rotax setup tool to the

dimension you quote because it is measuring in a different place, so can't

quote the equivalent figure for the 914.  Perhaps you have that figure to

pass on to the Forum.



--

brian.davies(at)clara.co.
Guest

Posted: Thu Jun 04, 2015 10:51 am Post subject: 912 rough running below 3000 rpm

Pete,



Page 30 in chapter 73-00-00 Heavy Maint Manual has the details.  I will try

to attach to this message.



Brian Davies



--

Rotax_Float_Lever001.pdf

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flynn elliott

Joined: 23 Jun 2007
Posts: 20
Location: SOUTH AFRICA

Posted: Mon Jun 08, 2015 4:18 am Post subject: 912 rough running below 3000 rpm

Hi Roger,

Carbs now stripped again, thoroughly cleaned out , new o rings ect.

Roughness at idle remains the same. Just for the hell of it we turned the

mixture screw in to lean the mixture, at just on 1/2 a turn out I now have a

very smooth idle ! rpm through the rest of the range is unafected. 

Will I be running the motor to lean , from what info I get the mixture screw

only effects low rpm operation i.e idle.

Thanks

Flynn

 



--

Otto Szorenyi

Joined: 10 Nov 2013
Posts: 3
Location: Maine

Posted: Mon Jun 08, 2015 5:35 am Post subject: 912 rough running below 3000 rpm

Flynn,



There is a product called "Colortune spark plug".

You can't use them under load but it's really neat device for setting

mixtures.

I used them extensively in the distant past tuning Weber and Dell'Orto

carbs.

Among others, Amazon sells them here

http://www.amazon.com/Colortune-for-14mm-Spark-Plug/dp/B000E9VGNM

This one's a 14mm thread size.



Regards,



Otto Szorenyi

--

Otto Szorenyi

Joined: 10 Nov 2013
Posts: 3
Location: Maine

Posted: Mon Jun 08, 2015 6:02 am Post subject: 912 rough running below 3000 rpm

Flynn,



While looking around on the Net I also found this interesting looking toy

that might interest you.



http://www.americanmuscle.com/plx-dm6-afr-sensor-module-combo.html



Otto S.



--

Roger Lee

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

Posted: Mon Jun 08, 2015 6:11 am Post subject: Re: 912 rough running below 3000 rpm

Hi Flynn,



The mixture screw is more for the low rpm.

When you cleaned the carbs did you remove the mixture screw on the bottom and blow through this orifice? Did you remove or at least blow through the mixture jet located in the corner of the bowl in both directions?



Is the mixture screw now out 1.5 turns and was it when all this started?



If you put a set of carb sync gauges on do the carbs sync at idle or is one carb considerably off over the other?

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

flynn elliott

Joined: 23 Jun 2007
Posts: 20
Location: SOUTH AFRICA

Posted: Mon Jun 08, 2015 7:49 am Post subject: 912 rough running below 3000 rpm

--

flynn elliott

Joined: 23 Jun 2007
Posts: 20
Location: SOUTH AFRICA

Posted: Mon Jun 08, 2015 7:51 am Post subject: 912 rough running below 3000 rpm

Thanks Otto.



--

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