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Carb Balancing

 
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Mallard



Joined: 22 Oct 2019
Posts: 27
Location: Ireland

PostPosted: Tue Sep 14, 2021 1:53 pm    Post subject: Carb Balancing Reply with quote

Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.

If you experienced a similar situation, how did you deal with it?

I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?
Thanks for any contributions.
James


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Area-51



Joined: 03 May 2021
Posts: 23

PostPosted: Tue Sep 14, 2021 11:44 pm    Post subject: Re: Carb Balancing Reply with quote

What input data at 3500rpm makes you think its a carburettor related issue?

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davidjoyce(at)doctors.org
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PostPosted: Wed Sep 15, 2021 1:29 am    Post subject: Carb Balancing Reply with quote

I would look seriously at the possibility that you have air leaking into the carburettor bowl. This now seems to be a fairly common issue with older 914s that still have the old paper gaskets. Typically folk spend months and a small fortune trying to work out what is happening before replacing the gaskets with the new Rotax rubber ones and ‘living happily ever after!’ Tends to produce very rough running at 3500+ rpm and reluctance to produce any greater revs - very disturbing if taking off from a short runway! Look out the article in Europa Flyer a year or two ago by Jim Butcher (assuming you are in the club it is available and searchable on the website). David Joyce, GXSDJ


On 2021-09-14 22:53, Mallard wrote:
Quote:
--> Europa-List message posted by: "Mallard" <james(at)kingdom.ie (james(at)kingdom.ie)>Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.If you experienced a similar situation, how did you deal with it?I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?Thanks for any contributions.James--------Seat of my pantsRead this topic online here:http://forums.matronics.com/viewtopic.php?p=503143#5bsp;--> http://www.matronics.com/Navigator= &nbspf="http://forums.matronics.com" target="_blank" rel="noopener noreferf="http://wiki.matronics.com" target="_blank" rel="noopener noreferre========================http://www.matronics=====================


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budyerly@msn.com



Joined: 05 Oct 2019
Posts: 144
Location: Florida USA

PostPosted: Wed Sep 15, 2021 2:13 am    Post subject: Re: Carb Balancing Reply with quote

Attached is a Rotax Troubleshooting guide that was updated this year.

Most likely if smooth at idle with good carb balance you may have any of a few other issues.

Spend time on the Rotax Owners.com and the videos. Rotax rebuild and tuning info is there. My article is long and boring also but may shed some insight.

Best Regards,
Bud Yerly


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Rotax Engine Troubleshooting Yerly April 2021.pdf
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h&jeuropa



Joined: 07 Nov 2006
Posts: 490

PostPosted: Wed Sep 15, 2021 3:18 am    Post subject: Re: Carb Balancing Reply with quote

Bud's troubleshooting guide is also available on the Europa Club website. You can use the search function on any page on the website to find information related to this problem.

Jim Butcher


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Gilles



Joined: 16 May 2020
Posts: 21

PostPosted: Wed Sep 15, 2021 3:23 am    Post subject: Carb Balancing Reply with quote

Le 14/09/2021 à 23:53, Mallard a écrit :

Quote:
Quote:
--> Europa-List message posted by: "Mallard" <james(at)kingdom.ie> (james(at)kingdom.ie)

Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.

If you experienced a similar situation, how did you deal with it?

I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?




Hi all,
Here is some info concerning our 914 UL and some other engines.
We never had any carb synch issues, but
1) We never disconnected the cables from the throttle levers.
2) We have a mechanical stop on the throttle lever so as to never exert any force to the carb lever stops. It is our experience that many buddies and hangar mates complaining about carb losing synch invariably happen to not have a stop on the lever, and so are likely to distort the carb lever stops.
Summarized some info here : http://contrails.free.fr/engine_rotax_stops.php
Among the carb issues we heard of, are the change in float bowl gasket thickness. An engine rough running was driving a buddy mechanic mad, until we discussed carb gaskets, and it appeared that some Rotax dealer-supplied gaskets were too thin, raising the bottom of the bowl too close to the main jet and impairing the flow into the main jet.
FWIW,

--
Best regards
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr


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wdaniell.longport(at)gmai
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PostPosted: Wed Sep 15, 2021 4:57 am    Post subject: Carb Balancing Reply with quote

I agree with David - I had air being sucked into my bowls but only above 11500.    Nitrile is the way to go.
William Daniell

LONGPORT

+1 786 878 0246
On Wed, Sep 15, 2021 at 5:32 AM <davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk)> wrote:

Quote:

I would look seriously at the possibility that you have air leaking into the carburettor bowl. This now seems to be a fairly common issue with older 914s that still have the old paper gaskets. Typically folk spend months and a small fortune trying to work out what is happening before replacing the gaskets with the new Rotax rubber ones and ‘living happily ever after!’  Tends to produce very rough running at 3500+ rpm and reluctance to produce any greater revs - very disturbing if taking off from a short runway! Look out the article in Europa Flyer a year or two ago by Jim Butcher (assuming you are in the club it is available and searchable on the website). David Joyce, GXSDJ  



On 2021-09-14 22:53, Mallard wrote:
Quote:
--> Europa-List message posted by: "Mallard" <james(at)kingdom.ie (james(at)kingdom.ie)>

Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.

If you experienced a similar situation, how did you deal with it?

I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?
Thanks for any contributions.
James

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Read this topic online here:

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Duncan McFadyean



Joined: 18 Jan 2011
Posts: 166

PostPosted: Wed Sep 15, 2021 7:29 am    Post subject: Carb Balancing Reply with quote

Or Viton.
Quote:
On 15 September 2021 at 13:57 William Daniell <wdaniell.longport(at)gmail.com> wrote:

I agree with David - I had air being sucked into my bowls but only above 11500. Nitrile is the way to go.
William Daniell

LONGPORT

+1 786 878 0246








On Wed, Sep 15, 2021 at 5:32 AM <davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk)> wrote:

Quote:

I would look seriously at the possibility that you have air leaking into the carburettor bowl. This now seems to be a fairly common issue with older 914s that still have the old paper gaskets. Typically folk spend months and a small fortune trying to work out what is happening before replacing the gaskets with the new Rotax rubber ones and ‘living happily ever after!’ Tends to produce very rough running at 3500+ rpm and reluctance to produce any greater revs - very disturbing if taking off from a short runway! Look out the article in Europa Flyer a year or two ago by Jim Butcher (assuming you are in the club it is available and searchable on the website). David Joyce, GXSDJ


On 2021-09-14 22:53, Mallard wrote:
Quote:
--> Europa-List message posted by: "Mallard" <james(at)kingdom.ie (james(at)kingdom.ie)>

Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.

If you experienced a similar situation, how did you deal with it?

I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?


Thanks for any contributions.
James

--------
Seat of my pants




Read this topic online here:

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Mallard



Joined: 22 Oct 2019
Posts: 27
Location: Ireland

PostPosted: Wed Sep 15, 2021 11:02 am    Post subject: Re: Carb Balancing Reply with quote

Thanks for your assistance David but fortunately the problem isn't as bad as that, at least not yet! The engine is producing normal power all the way from idle up to & including turbo boost. It just runs a bit rough (at) 3500rpm. We didn't notice it while flying & only spotted it while sitting on the ground & holding the throttle steady (at) 3500rpm.

Btw, during the last annual inspection the Carb floats were changed by my engineer using the Rotax supplied (foc) kit which I'm fairly sure included the Rubber gaskets.

Also,
When we balanced the carbs we stopped all the vibrations which were present pretty much throughout the full rpm range. The vibrations were so bad it initially felt like the prop was out of balance.

Regards
James
davidjoyce(at)doctors.org wrote:
I would look seriously at the possibility that you have air leaking into the carburettor bowl. This now seems to be a fairly common issue with older 914s that still have the old paper gaskets. Typically folk spend months and a small fortune trying to work out what is happening before replacing the gaskets with the new Rotax rubber ones and &lsquo;living happily ever after!&rsquo; Tends to produce very rough running at 3500+ rpm and reluctance to produce any greater revs - very disturbing if taking off from a short runway! Look out the article in Europa Flyer a year or two ago by Jim Butcher (assuming you are in the club it is available and searchable on the website). David Joyce, GXSDJ


On 2021-09-14 22:53, Mallard wrote:
Quote:
--> Europa-List message posted by: "Mallard" <james>Has anyone had the experience of balancing the carbs on a Rotax 912 type engine and after a couple of hours of smooth running across all revs you suddenly get rough running at 3500 rpm.If you experienced a similar situation, how did you deal with it?I'd also be interested to hear from any 914 owners on the forum who have had the above 'Carb Balancing' problems & what was done to keep the Carbs Balanced?Thanks for any contributions.James--------Seat of my pantsRead this topic online here:http://forums.matronics.com/viewtopic.php?p=503143#5bsp;--> http://www.matronics.com/Navigator= &nbspf="http://forums.matronics.com" target="_blank" rel="noopener noreferf="http://wiki.matronics.com" target="_blank" rel="noopener noreferre========================http://www.matronics=====================


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