Matronics Email Lists :: View topic - rough running at 3400 RPM and above

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

rough running at 3400 RPM and above
Goto page Previous 1, 2

Matronics Email Lists Forum Index -> RotaxEngines-List

View previous topic :: View next topic

Author Message

Tommy Walker

Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207

Posted: Sat Aug 07, 2010 5:05 am Post subject: Re: rough running at 3400 RPM and above

Doug,



Glad to hear you got the rotax running smooth now.

When do  you think you will get in the air?



I am starting a Kitfox SS7 next week, so have left the Zenith world.  Going with a continental on this one, but would swap it for a Rotax.



Take care,



Tommy Walker in Alabama

_________________
Tommy Walker
N25A - Anniston, AL

kyle Ponsford

Joined: 17 Aug 2014
Posts: 3

Posted: Tue Aug 19, 2014 9:06 am Post subject: Re: rough running at 3400 RPM and above

Doug,

Your descriptions read as if I had written them myself, therefore I was very eager to read to the bottom and see your eventual solution, but I found... NOTHING!

Did you ever solve your problem? I have not.



My early model  Rotax 912UL with Bing 64 carbs runs very smooth up to 3500 RPM but after that it stumbles/vibrates so badly that it looses power and refuses to push through 4100. but when I pull carb-heat it immediately smooths out and allows me to push it to 4300 RPMs for short periods before falling off dramatically. With the carb-heat "solution" I too came to the early opinion that I was running lean.

But I have one significant difference from yours: my plugs are so sooty black they foul about every third flight when I change them. Which leads me to think our identical problems are not plug or fuel related.

(I had been running rich plugs to attempt to balance my white #4 cylinder plug due to a factory recognized poor design of the intake header. I have since changed my strategy but that is another issue).



I have torn apart my fuel system from one end to the other, cleaned carbs, checked jets, replaced seals and vitnum tipped needles, reset float levels, changed plugs and adjusted plug gaps many times, re-attached the plug wires in their seats and boots, etc. etc.

Each time I spend days messing with it until I seem to have solved the problem, go for a few flights before the problem comes back, first small vibrations at the higher end, then more significant vibrations and at progressively lower RPMs until it becomes unflyable again. This has gone on for three years and has greatly mangled my enthusiasm for flying as it keeps me circling my private strip in frustration.



Speculations:

Recently I had a loose alternator belt on my truck and the engine started to loose power and run very poorly but it continued to run at low RPMs.

I tightened the belt and solved my problem.

It got me to thinking that I may be having a similar problem with my magnetos. This is so recent a thought that I have not yet began to explore how to check my mags when the engine won't run in the region that needs testing.

Then I found your thread here.

PLEASE tell me you finally figured out the actual solution but failed to post it here! I am very, very interested.



- Kyle

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Aug 19, 2014 10:44 am Post subject: rough running at 3400 RPM and above

My first flight to Alaska in 1994, my 912 had a similar problem.  



Eventually raised the fuel needles one notch and corrected the problem.

Seems the old 80 horse is really sensitive to lean conditions at midrange.



The way I eventually discovered the fix was pulling the enricher full on

during flight at about 4,200 rpm.  The engine gained 200 rpm.  



john h

mkIII

Titus, Alabama



--

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

joeing701(at)simnet.is
Guest

Posted: Tue Aug 19, 2014 12:49 pm Post subject: rough running at 3400 RPM and above

Hello Kyle.  

My friend had the exact same problem you have. He had been messing with his Rotax 912 ul engine since he bought it. Same as your experiance, seemed to have solved it but the rough running always came back. Finally he found the problem. The Stator was the original part and had been a recallmon that part, but it had not been replaced at the correct time.

So my advice is to replace the stator. You can find the recall information from the Rotax on the stator.

Hope this helps,

Johann G.



Sent from my iPad



 	  Quote: 	
		   On Aug 19, 2014, at 5:06 PM, "kyle Ponsford" <wild_kyle(at)hotmail.com> wrote:

 

 

 

 Doug,

 Your descriptions read as if I had written them myself, therefore I was very eager to read to the bottom and see your eventual solution, but I found... NOTHING!

 Did you ever solve your problem? I have not.

 

 My early model  Rotax 912UL with Bing 64 carbs runs very smooth up to 3500 RPM but after that it stumbles/vibrates so badly that it looses power and refuses to push through 4100. but when I pull carb-heat it immediately smooths out and allows me to push it to 4300 RPMs for short periods before falling off dramatically. With the carb-heat "solution" I too came to the early opinion that I was running lean.

 But I have one significant difference from yours: my plugs are so sooty black they foul about every third flight when I change them. Which leads me to think our identical problems are not plug or fuel related.

 (I had been running rich plugs to attempt to balance my white #4 cylinder plug due to a factory recognized poor design of the intake header. I have since changed my strategy but that is another issue).

 

 I have torn apart my fuel system from one end to the other, cleaned carbs, checked jets, replaced seals and vitnum tipped needles, reset float levels, changed plugs and adjusted plug gaps many times, re-attached the plug wires in their seats and boots, etc. etc.

 Each time I spend days messing with it until I seem to have solved the problem, go for a few flights before the problem comes back, first small vibrations at the higher end, then more significant vibrations and at progressively lower RPMs until it becomes unflyable again. This has gone on for three years and has greatly mangled my enthusiasm for flying as it keeps me circling my private strip in frustration.

 

 Speculations:

 Recently I had a loose alternator belt on my truck and the engine started to loose power and run very poorly but it continued to run at low RPMs.

 I tightened the belt and solved my problem.

 It got me to thinking that I may be having a similar problem with my magnetos. This is so recent a thought that I have not yet began to explore how to check my mags when the engine won't run in the region that needs testing.

 Then I found your thread here.

 PLEASE tell me you finally figured out the actual solution but failed to post it here! I am very, very interested.

 

 - Kyle

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=428766#428766

kyle Ponsford

Joined: 17 Aug 2014
Posts: 3

Posted: Tue Aug 19, 2014 3:22 pm Post subject: Re: rough running at 3400 RPM and above

Johann G.,

I am grateful for your information/suggestion and will tackle that idea immediately!

Thanks,

- Kyle

vernon11

Joined: 03 Aug 2010
Posts: 14

Posted: Wed Aug 20, 2014 5:03 am Post subject: rough running at 3400 RPM and above

Kyle.

       I might have missed something, but have you had the carbs balanced. I 

had all sorts of drama, until the carbs were balanced.

Good luck.

Vernon.

South Africa.



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

From: "kyle Ponsford" <wild_kyle(at)hotmail.com>

Sent: Wednesday, August 20, 2014 1:22 AM

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

Subject: Re: rough running at 3400 RPM and above



 	  Quote: 	
		   

 <wild_kyle(at)hotmail.com>



 Johann G.,

 I am grateful for your information/suggestion and will tackle that idea 

 immediately!

 Thanks,

 - Kyle





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=428799#428799

kyle Ponsford

Joined: 17 Aug 2014
Posts: 3

Posted: Fri Aug 22, 2014 10:42 am Post subject: Re: rough running at 3400 RPM and above

Update:

Investigating the idea that my problem was the Stator, I was eventually led to Lockwood Aviation in Sebring Florida and spoke to their technician named Kerry, who, really impressed me with his knowledge and confidence in explaining, first; that my Stator was fine, and second; what my problem was.



For those curious about both issues:

The stator has two functions; providing power to the magnetos, and charging the battery. When it fails the first, the engine just quits. when it fails the second the battery won't charge.

I have neither symptom.



Kerry convinced me that my entire problem was carburetor related. It seems that Vernon (along with several others) are correct.

My "unsolvable" problem has been in a lack of understanding the distinction between Synchronizing and Balancing when everyone seemed to use the words interchangeably, such as sync/balance. So now that I know there is a difference, let me explain for others, who, like me, are confused in thinking they are one in the same.



I am familiar with syncing carbs on my snowmachine. Yes I have done this with my airplane... several times. So, I was convinced that "Yes, I have done that, thank you very much," ...but in fact, I had not balanced my carbs. It appears that this is my problem. (I have sent Kerry my carbs for a complete "fresh start" rebuild and will Post my results when I get them remounted and balanced).



So here is the short of synchronizing carbs: It is the adjustment of the throttle cables to ensure that both carb slides open at the same amount at the same time. I am very careful to do this as accurately as possible and after setting, this should remain continuous until disconnecting the throttle cables for any reason. To me, this is a "one time event," though in my desperation I have checked and rechecked them and found them fine.



BUT: balancing carbs is adjusting the fuel screws between carbs so that they suck the same. This takes a set of vacuum gauges or even a simple home-made set of water bottles explained on youtube. This is something that needs regular rechecks as it changes with vibration and such.

I confess, I have never balanced my carbs, but now intend to make this a regular maintenance procedure.



As I said, I will post my results when I get my carbs back and reinstalled, but at this point I am confident that I finally understand my problem,

perhaps this can help others too.



- Kyle

kerrimikehickman(at)aol.c
Guest

Posted: Fri Aug 22, 2014 11:03 am Post subject: rough running at 3400 RPM and above

Balancing is great (I personally always referred to it as 'syncing' after 'adjusting' the idle/full throttle throws) but I'm not a 912 mechanic either... 

  I'd recommend the Rotax-owners.com website for a wealth of information if you've not been there. 

  Although balancing can be accomplished many ways I personally highly recommend the Carbmate. It made it so quick and "stupid" easy I balance my carbs much more often which has helped make a very noticeable difference in my 912 performance year-round. Costs $100 bucks but immeasurably worth in to me.

 Mike

  --

Roger Lee

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

Posted: Sat Aug 23, 2014 4:18 pm Post subject: Re: rough running at 3400 RPM and above

Even though the Carbmate and Syncromate can split a hair what they can't do at all is diagnose several carb problems at a glance or just by looking can't tell you which carb to adjust, which way and by approximately how much. They can't tell you if the cable needs to be lengthened or shortened at the throttle arm, but only that they are out of sync. 



They do work well, but after you disconnect the electronic device and hook the carbs back up the hair splitting is gone.



I think the analog gauges still hold a distinct advantage over the electronic balancer's and in many Rotax classes we have come to the same conclusion.

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

JohnF

Joined: 13 May 2010
Posts: 124

Posted: Sat Aug 23, 2014 4:55 pm Post subject: Re: rough running at 3400 RPM and above

Roger, why don't you out together a kit of the gauges you use and offer it for sale?  I'd probably buy one

johnwf

dougsnash

Joined: 14 Apr 2008
Posts: 281

Posted: Sun Aug 24, 2014 4:51 am Post subject: rough running at 3400 RPM and above

All applicable kudos to Roger if he does decide to produce a gauge set for syncing 912/914 carbs but it would be a redundant product.  Lockwood sells a very nice analog gauge set with applicable hoses, valves, and fittings for about $90.00.  I purchased one about five years ago and have used it several times.

http://www.lockwood.aero/p-2586-carb-synchronization-kit-for-rotax-912914.aspx

Doug M



Time: 05:55:37 PM PST US

Subject: RotaxEngines-List: Re: rough running at 3400 RPM and above

From: "JohnF" <n29cx(at)ridgeviewtel.us (n29cx(at)ridgeviewtel.us)>

Roger, why don't you out together a kit of the gauges you use and offer it for

sale?  I'd probably buy one

johnwf



    

 [quote][b]

Roger Lee

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

Posted: Sun Aug 24, 2014 5:09 am Post subject: Re: rough running at 3400 RPM and above

Gauges are all over the market as some have pointed out. All you need is 2 vacuum gauges that go from 0 to 30 in. I prefer liquid filled gauges.Buy some vacuum tubing from the auto store or Ace Hardware )about 10'), buy two needle valves from Ace (install them about 6" from the gauges) and then buy a 3/8" barbed fitting and reducers to fit the small vacuum tube (sand off the barbs so it is smooth), then get a 6" piece of poly tubing to fit on the other vacuum tube. 

When you sync the carbs push off the left or right side rubber hose that is on the carb balance tube. Now the carbs are separated. Then put the smooth brass end in the rubber hose and slide the poly hose over the 90 degree fitting on top of the air intake.



Start your engines!



p.s.

The clear hose in the picture is for demo and it should be regular vacuum hose.



With gauges like these you can diagnose many carb issues and balance is faster because you can instantly see which carb needs what. Once in a while simple is better.



If you really wanted a carb sync tool on steroids put these gauges inline with an electronic model and you could have both worlds at your finger tips, but would be a little bulky and you would still need to hook the electronic one to the battery. I have seen 1-2 like that.

carb_sync_150.jpg

Description:

Easy to make carb sync tool

Filesize:

120.66 KB

Viewed:

14694 Time(s)

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

Ollie Washburn

Joined: 10 Jan 2006
Posts: 56
Location: Central Florida

Posted: Sun Aug 24, 2014 9:57 am Post subject: rough running at 3400 RPM and above

And the best thing I have found to use is a twin engine manifold press. gage.

   Ollie



Sent from my iPad



 	  Quote: 	
		   On Aug 23, 2014, at 8:18 PM, "Roger Lee" <ssadiver1(at)yahoo.com> wrote:

 

 

 

 Even though the Carbmate and Syncromate can split a hair what they can't do at all is diagnose several carb problems at a glance or just by looking can't tell you which carb to adjust, which way and by approximately how much. They can't tell you if the cable needs to be lengthened or shortened at the throttle arm, but only that they are out of sync. 

 

 They do work well, but after you disconnect the electronic device and hook the carbs back up the hair splitting is gone.

 

 I think the analog gauges still hold a distinct advantage over the electronic balancer's and in many Rotax classes we have come to the same conclusion.

 

 --------

 Roger Lee

 Tucson, Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Repair Center - Heavy Maint. Rated

 Home 520-574-1080  TRY HOME FIRST

 Cell 520-349-7056

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=429192#429192

_________________
Ollie RV6-A & Rans S7S
Central FL

Display posts from previous:

	Matronics Email Lists Forum Index -> RotaxEngines-List	All times are GMT - 8 Hours Goto page Previous 1, 2
Page 2 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum