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joeing701(at)simnet.is
Guest

Posted: Sat Nov 20, 2010 10:39 am Post subject: Rough running cured with carb heater

Hello list members.



I have a friend who has been having problems with the Rotax 912 UL in  

a Kitfox 3.  When flying today in a temp. around 40°F, the engine ran  

rough until he pulled the carb heat on. Ran very smooth and never as  

good.

What do you think could cause this problem? We measured the carb  

levels and they are very similar. 1/8 of an inch. One carb was  

definitely running bad because the EGT dropped on one exhaust.

No carb ice and the carbs have been rebuild. Any ideas?



Johann G.

Iceland.

Zenith 701

Rotax 912UL.

cscsail(at)gmavt.net
Guest

Posted: Sat Nov 20, 2010 2:56 pm Post subject: Rough running cured with carb heater

Carb heat bypasses the air filter, at least on most set-ups, so maybe a 

clogged filter.

It also introduces warm air which is less dense, so it could be that the 

mixture of one or both carbs is set to lean for the normal (cold) air --my 

guess.

Gordon

---

joeing701(at)simnet.is
Guest

Posted: Sat Nov 20, 2010 3:27 pm Post subject: Rough running cured with carb heater

Thank you Gordon.

I know my friend has a new air filter and the airbox does eliminate  

the cold air from the filter and only passes the hot air from the  

exhaust pipe. We will look at the mixture setting.

Thanks again.



Johann G.

Iceland.

On 20.11.2010, at 22:49, Gordon wrote:



[quote] 



 Carb heat bypasses the air filter, at least on most set-ups, so  

 maybe a clogged filter.

 It also introduces warm air which is less dense, so it could be that  

 the mixture of one or both carbs is set to lean for the normal  

 (cold) air --my guess.

 Gordon

 ---

Roger Lee

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

Posted: Sat Nov 20, 2010 3:29 pm Post subject: Re: Rough running cured with carb heater

Three things I would do. 

Have the carbs been pneumatically balanced? If yes move on, if no do it.

Are the carb vent tubes in their proper place? Check these to see if one moved.

When the carbs were rebuilt did the person put the diaphragm notch in the proper place? You will need to pull the top off each carb to check this, but this is easy.

Clogged filter as suggested maybe, but I don't think of Iceland as being really dusty. It takes quite a bit to cause this. If you are using a K&N filter and over saturate it with oil this will cause a leaning issue and opening the carb heat would let in more air. What type of airbox does it have? A standard Rotax airbox or two individual filters?



When you say carb levels do you mean float levels? Whom ever rebuilt these should have checked the float arm measurement when he rebuilt these. If he didn't this may cause a rough running carb.

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

joeing701(at)simnet.is
Guest

Posted: Sat Nov 20, 2010 3:55 pm Post subject: Rough running cured with carb heater

Hello Roger.



Thank you very much for all these points. We will check on them all.  

Not sure how the vent tubes are on his plane. Easy to find out  

tomorrow. The diaphragms are new and are correctly installed in the  

notch. He is using one big K&N filter and it is clean. Yes, I meant to  

say the float level. The Airbox is something made by the builder.  

Maybe it is not working properly. I think it is a standard item for  

the Kitfox. First we will do the balancing again, and check the vent  

tubes.



Thanks again.



Johann G.

Iceland.



On 20.11.2010, at 23:29, Roger Lee wrote:



 	  Quote: 	
		   

 >



 Three things I would do.

 Have the carbs been pneumatically balanced? If yes move on, if no do  

 it.

 Are the carb vent tubes in their proper place? Check these to see if  

 one moved.

 When the carbs were rebuilt did the person put the diaphragm notch  

 in the proper place? You will need to pull the top off each carb to  

 check this, but this is easy.

 Clogged filter as suggested maybe, but I don't think of Iceland as  

 being really dusty. It takes quite a bit to cause this. If you are  

 using a K&N filter and over saturate it with oil this will cause a  

 leaning issue and opening the carb heat would let in more air. What  

 type of airbox does it have? A standard Rotax airbox or two  

 individual filters?



 When you say carb levels do you mean float levels? Whom ever rebuilt  

 these should have checked the float arm measurement when he rebuilt  

 these. If he didn't this may cause a rough running carb.



 --------

 Roger Lee

 Tucson, Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Repair Center

 Home 520-574-1080  TRY HOME FIRST

 Cell 520349-7056





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=320201#320201

blackmore(at)platinum.ca
Guest

Posted: Sat Nov 20, 2010 5:24 pm Post subject: Rough running cured with carb heater

joeing701(at)simnet.is
Guest

Posted: Sun Nov 21, 2010 3:08 am Post subject: Rough running cured with carb heater

Hello Chris.



Can you send me your message again. I did not receive any text with it.



Best regards,

Johann G.

Iceland.

On 21.11.2010, at 01:20, Chris Blackmore wrote:



 	  Quote:

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Nov 21, 2010 7:49 am Post subject: Rough running cured with carb heater

40F  no doubt about it you had carb ice which obstructed the flow of fuel.

Let me guess your engine has an airbox feeding the carbs.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Nov 21, 2010 8:01 am Post subject: Rough running cured with carb heater

Apparently icing is mostly experienced with 912s which have the airbox.

Engines with direct filtration almost never experience ice...  go figure.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

joeing701(at)simnet.is
Guest

Posted: Sun Nov 21, 2010 9:51 am Post subject: Rough running cured with carb heater

Hello all,

Yes Noel, my friend has the airbox on his Kitfox. He did a few checks  

today as recommended by Roger and Gordon.

Carbs were adjusted and balanced. The mixture on the jet needles/ 

needle jets were enriched and are now in the bottom groove on the  

needle.

The diaphragm is properly installed and the propeller is set for the  

correct rpm. We even tried to remove the air hoses from the carbs to  

eliminate carb ice. No change.

The engine runs fine on the low rpm but will not run smooth unless the  

carb heat is used.

The needles are all standard as recommended by Rotax.

Any more advice will be really appreciated,



Best regards,

Johann G.

Iceland.



On 21.11.2010, at 15:57, Noel Loveys wrote:



[quote] 

 >



 Apparently icing is mostly experienced with 912s which have the  

 airbox.

 Engines with direct filtration almost never experience ice...  go  

 figure.



 Noel



 --

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Nov 23, 2010 8:13 am Post subject: Rough running cured with carb heater

I only mentioned the airbox because history weems to prove the 912 is much

more susceptible to cerb icing when the airbox is installed.  If the two

individual filters ate installed then the problem with carb icing doesn't

seem to occur for some reason.  Certainly if you notice the engine running

rough and pulling the carb heat clears it in about five minutes ( it isn't

an immediate clearing ) then you have experienced carb ice.



The only thing wrong with it is you have to depend upon another piece of

equipment to keep your engine running but guys have been doing that with

carb heat since WW 1.



The only trick to using carb heat is to pull it on as soon as  you notice a

roughness in the engine and then give it time to work.  Yes Carb heat does

use a non-filtered air supply but the filtration of that air supply is only

a screen.  Screens have been closed off in the past with impact ice.  So if

you see impact ice expect a problem there.  More often than not impact ice

occurs when encountering freezing rain.  In that case you climb as fast as

you can.  Freezing rain occurs when you have a temperature inversion and

climbing will bring you into warmer air...  Mind, you may not have a lot of

time to make the decision to climb  so the best thing to do is avoid

freezing rain at all times.  I have already lost a friend to freezing

rain.... He was flying a Grumman Widgeon...Full IFR.



A few years ago a young local cadet was taking her father for his first ride

in a small plane when she ran into engine trouble.  She pulled the carb

heat...nothing,  so she set up a forced approach on the main drag of a small

town which she expertly manoeuvred missing several power lines crossing the

road.  Once on the ground the engine started and ran perfectly.  If she had

left the carb heat on and the engine running it would have cleared itself.

The plane still had to be disassembled to be returned to the airport. 



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

joeing701(at)simnet.is
Guest

Posted: Tue Nov 23, 2010 9:51 am Post subject: Rough running cured with carb heater

Hello Noel.



Thank you for the advice.

I think my friend will just fly with the carb heat on until he can get  

a new set of jet needles and needle jets that will give him a richer  

mixture. The plane originally came from the south region of the US,  

and I do believe that the second owner,

whom my friend bought the plane from, never did get it to run  

properly. He lived in the Pennsylvania area. I know there were other  

problems that were not dealt with by him, but my friend has fixed a  

few item which would have cause a rough and bad running of the engine.

The carb heat setting cures the rough running as soon as it is turned  

on. No delay or melting of ice. This is mostly during engine run-up on  

the ground.

If anyone knows of a way to eliminate the heat box and install the K&N  

filters directly to the carbs on a Kitfox 3, please keep me informed.

My set-up on the Zenith 701 has never cause carb ice, at least never  

that I have notice.



Best regards,

Johann G.

Iceland.

On 23.11.2010, at 16:01, Noel Loveys wrote:



 	  Quote: 	
		   

 >



 I only mentioned the airbox because history weems to prove the 912  

 is much

 more susceptible to cerb icing when the airbox is installed.  If the  

 two

 individual filters ate installed then the problem with carb icing  

 doesn't

 seem to occur for some reason.  Certainly if you notice the engine  

 running

 rough and pulling the carb heat clears it in about five minutes ( it  

 isn't

 an immediate clearing ) then you have experienced carb ice.



 The only thing wrong with it is you have to depend upon another  

 piece of

 equipment to keep your engine running but guys have been doing that  

 with

 carb heat since WW 1.



 The only trick to using carb heat is to pull it on as soon as  you  

 notice a

 roughness in the engine and then give it time to work.  Yes Carb  

 heat does

 use a non-filtered air supply but the filtration of that air supply  

 is only

 a screen.  Screens have been closed off in the past with impact  

 ice.  So if

 you see impact ice expect a problem there.  More often than not  

 impact ice

 occurs when encountering freezing rain.  In that case you climb as  

 fast as

 you can.  Freezing rain occurs when you have a temperature inversion  

 and

 climbing will bring you into warmer air...  Mind, you may not have a  

 lot of

 time to make the decision to climb  so the best thing to do is avoid

 freezing rain at all times.  I have already lost a friend to freezing

 rain.... He was flying a Grumman Widgeon...Full IFR.



 A few years ago a young local cadet was taking her father for his  

 first ride

 in a small plane when she ran into engine trouble.  She pulled the  

 carb

 heat...nothing,  so she set up a forced approach on the main drag of  

 a small

 town which she expertly manoeuvred missing several power lines  

 crossing the

 road.  Once on the ground the engine started and ran perfectly.  If  

 she had

 left the carb heat on and the engine running it would have cleared  

 itself.

 The plane still had to be disassembled to be returned to the airport.



 Noel

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Nov 23, 2010 1:45 pm Post subject: Rough running cured with carb heater

If no delay then it is probably an obstruction in the air intake.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

joeing701(at)simnet.is
Guest

Posted: Tue Nov 23, 2010 2:50 pm Post subject: Rough running cured with carb heater

Thank you Noel.



We will look into that. The filter is new and clean. But there must be  

a reason for the warm air requirement in his setup.

He spent all last summer and the winter so far to try to figure this  

out with no avail. Very frustrating.



Best regards.

Johann G.



On 23.11.2010, at 21:38, Noel Loveys wrote:



[quote] 

 >



 If no delay then it is probably an obstruction in the air intake.



 Noel



 --

joeing701(at)simnet.is
Guest

Posted: Tue Nov 23, 2010 3:06 pm Post subject: Rough running cured with carb heater

Hello Rick.

Thanks for the advice. Yes, he would never fly the plane if it was dangerous. The problem with crating the engine and sending it to an authorized repair station would almost cost him the same as a new engine. There is no authorized repair station here in Iceland.

It would have to be shipped to Europe (the mainland) or the US for repair. The shipping cost and other taxing cost is very high plus the repair cost would not be inexpensive either. We know that the engine is not the problem, but the setup of the carbs, cables and/or air intake.

We may just remove the carbs from my plane and try them on his plane before we do anything else. This way we could eliminate the carbs and safe us a lot of work. A lot less expensive than to remove the whole engine of the plane and ship it. 

The isolation here is our biggest problem in the ultralight and aviation hobby in Iceland. Everything is taxed with 25% sales tax and our currency is very low value compared to the $.

I will keep you posted of our progress.

Thank you all who have helped with their solutions.

Johann G.

Iceland. 



On 23.11.2010, at 18:49, Richard Girard wrote:

[quote]Johann, Please try to convince your friend to ground his airplane until the source of this problem is found. That you have a marginal fix only means that by flying with it in that configuration you are removing that from your possibilities should an inflight emergency arise. Aircraft accidents are generally not made of One Big Thing going wrong, but rather a series of small things that by themselves are manageable, but when combined at the wrong moment bring disaster. Attacking the jetting is most probably the wrong thing to do, as well. There are literally thousands of these engines flying with only minor adjustments to the clip setting of the jet needle, and those are almost always to go leaner, not richer.

 If your friend cannot solve this problem, try to convince him to remove the engine, crate it up and send it an authorized repair station where they can diagnose it properly.

My 2 cents.

 Rick Girard



2010/11/23 Jóhann Jóhannsson <joeing701(at)simnet.is (joeing701(at)simnet.is)>

 	  Quote: 	
		   --> RotaxEngines-List message posted by: =?ISO-8859-1?Q?J=F3hann_J=F3hannsson?= <joeing701(at)simnet.is (joeing701(at)simnet.is)>

 

 Hello Noel.

 

 Thank you for the advice.

 I think my friend will just fly with the carb heat on until he can get a new set of jet needles and needle jets that will give him a richer mixture. The plane originally came from the south region of the US, and I do believe that the second owner,

 whom my friend bought the plane from, never did get it to run properly. He lived in the Pennsylvania area. I know there were other problems that were not dealt with by him, but my friend has fixed a few item which would have cause a rough and bad running of the engine.

 The carb heat setting cures the rough running as soon as it is turned on. No delay or melting of ice. This is mostly during engine run-up on the ground.

 If anyone knows of a way to eliminate the heat box and install the K&N filters directly to the carbs on a Kitfox 3, please keep me informed.

 My set-up on the Zenith 701 has never cause carb ice, at least never that I have notice.

 

 Best regards,

 Johann G.

 Iceland.

 

 

 On 23.11.2010, at 16:01, Noel Loveys wrote:

 

  	  Quote: 	
		   --> RotaxEngines-List message posted by: "Noel Loveys" <noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)>

 

 I only mentioned the airbox because history weems to prove the 912 is much

 more susceptible to cerb icing when the airbox is installed.  If the two

 individual filters ate installed then the problem with carb icing doesn't

 seem to occur for some reason.  Certainly if you notice the engine running

 rough and pulling the carb heat clears it in about five minutes ( it isn't

 an immediate clearing ) then you have experienced carb ice.

 

 The only thing wrong with it is you have to depend upon another piece of

 equipment to keep your engine running but guys have been doing that with

 carb heat since WW 1.

 

 The only trick to using carb heat is to pull it on as soon as  you notice a

 roughness in the engine and then give it time to work.  Yes Carb heat does

 use a non-filtered air supply but the filtration of that air supply is only

 a screen.  Screens have been closed off in the past with impact ice.  So if

 you see impact ice expect a problem there.  More often than not impact ice

 occurs when encountering freezing rain.  In that case you climb as fast as

 you can.  Freezing rain occurs when you have a temperature inversion and

 climbing will bring you into warmer air...  Mind, you may not have a lot of

 time to make the decision to climb  so the best thing to do is avoid

 freezing rain at all times.  I have already lost a friend to freezing

 rain.... He was flying a Grumman Widgeon...Full IFR.

 

 A few years ago a young local cadet was taking her father for his first ride

 in a small plane when she ran into engine trouble.  She pulled the carb

 heat...nothing,  so she set up a forced approach on the main drag of a small

 town which she expertly manoeuvred missing several power lines crossing the

 road.  Once on the ground the engine started and ran perfectly.  If she had

 left the carb heat on and the engine running it would have cleared itself.

 The plane still had to be disassembled to be returned to the airport.

 

 Noel

 

 

 

 	
 

 

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[b]

Roger Lee

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

Posted: Tue Nov 23, 2010 5:40 pm Post subject: Re: Rough running cured with carb heater

Hi Johann,



I don't think it has anything to do with the warm air, but just more air in general.

_________________
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: Wed Nov 24, 2010 5:21 am Post subject: Re: Rough running cured with carb heater

Johann,



If you find that your carburetors work fine on his engine, then it is time for you to take his carburetors apart for a thorough cleaning and inspection. You don't have to be a certified mechanic to do this, just be able to follow instructions well and carefully, and take your time. You can buy the Bing Carburetor manual for $11 in the US or maybe better to buy it from the factory, since you are in Iceland. It goes in to all the detail you need to dis-assemble, clean and inspect the carburetors.



I have found that aircraft that have been through multiple owners have sometimes had unqualified mechanics "fixing" carb problems that they did not really understand, by changing jets that should not have been changed. I've even seen this in Type Certificated aircraft with Certified Rotax 912 engines. Once you are certain that all the jets, needles, and seals are correct and in good condition and the adjustments are according to the Rotax recommendations, and the carbs balanced/synchronized properly, your problems will likely disappear. 



Trust the manufacturer to know his engine better than anyone else, and follow their advice.



Thom Riddle

Buffalo, NY

USA

http://sites.google.com/site/riddletr/a&pmechanix

_________________
Thom Riddle
Buffalo, NY (9G0)

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

Dick Maddux

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

Posted: Wed Nov 24, 2010 5:46 am Post subject: Rough running cured with carb heater

Johann,

  Applying carb heat in most aircraft leans the mixture . Perhaps you are running on the rich side now and by applying carb heat you lean the mixture and the engine runs better ? 

 Or as Roger says,"not enough air with more throttle" ?

  I haven't followed your listing too closely so have probably missed something. I doubt adjusting the needles would make that much difference but you could try going to a leaner position & see if that helps.

  My 2 cents

                                                      Dick Maddux

                                                      912UL

                                                      Milton,Fl 

 [quote][b]

Thom Riddle

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

Posted: Wed Nov 24, 2010 6:04 am Post subject: Re: Rough running cured with carb heater

Dick,



...Applying carb heat in most aircraft leans the mixture ...



I regret to inform you that you are mistaken. The warmer less dense air from applying carb heat, combined with the same amount of fuel, results in a richer mixture, not leaner. This is why as you climb higher into less dense air you must lean the mixture to maintain proper combustion.

_________________
Thom Riddle
Buffalo, NY (9G0)

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

daveaustin2(at)primus.ca
Guest

Posted: Wed Nov 24, 2010 9:37 am Post subject: Rough running cured with carb heater

Thom,

If the air is hotter and less dense, will it not raise the needle as far, and thus lean the mixture? 

That would also apply as you fly higher.

Dave Austin

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