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Rough Running 912 UL

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experimental208nd(at)comc
Guest

Posted: Tue Nov 07, 2006 8:03 pm Post subject: Rough Running 912 UL

Hi List,

 I have a 912 UL with 145 tthours. It had a rough spot at  about 3000-3200 rpms on the ground or in the air. 

 I have checked and regapped the plugs to .028,  

 cleaned out the bowls on the carbs,

 cleaned off the neddle and dome area, sanded the ground  wire lugs for the coils to get a good ground.

 Checked the carb Ballance -its ok.

 It all has not helped at all, even makes the rough ness  worse some times. Going from 2k rpms- 3k rpms it is almost like it is bogging  down, and you have to sort of pump the throttle to get the rpms past the 3-3.2 k  mark.

  

 Doing the mag check it is very rough on each side also,  and I am using gas with the 10 % methanol( exact amount unknown )

  

 My qquestion is any ideas on the cause, there was no  visible dirt or matter in the bowls either?????

  

 I am going to try and put in new plugs and then try some  AV gas instead.

  

 Let me know what you think

 Thanks

 Jay

  

   [quote][b]

propellerdesign(at)tele2.
Guest

Posted: Tue Nov 07, 2006 11:58 pm Post subject: Rough Running 912 UL

To me it sounds (without hearing the engine) that  it get to little fuel at that rpm range, can also be to rich.

 Idle adjustment?

 carb diaphragm?

 Leaking inlet tubes?

 dirt in the middle range system?

  

 Jan Carlsson

 jcpropellerdesign.com

  

 [quote]   ---

dcsfoto

Joined: 24 Aug 2006
Posts: 120

Posted: Wed Nov 08, 2006 5:59 am Post subject: Re: Rough Running 912 UL

my 912 runs good but in if I try to run in the 3000-3200 range it seems to run rough or vibrate more. I just avoid that rpm spot

smokey_bear_40220(at)yaho
Guest

Posted: Wed Nov 08, 2006 7:24 am Post subject: Rough Running 912 UL

Sounds lean and not safe to fly.  Make sure you get

that fixed first.  You may be a bit lean overall and

that range is just the worst of the bunch.  How are

your EGT´s?



Kurt S.  S-5



--- Jay Fabian <experimental208nd(at)comcast.net> wrote:



 	  Quote: 	
		   Hi List,

 I have a 912 UL with 145 tthours. It had a rough

 spot at about 3000-3200 rpms on the ground or in the

 air. 

 I have checked and regapped the plugs to .028, 

 cleaned out the bowls on the carbs,

 cleaned off the neddle and dome area, sanded the

 ground wire lugs for the coils to get a good ground.

 Checked the carb Ballance -its ok.

 It all has not helped at all, even makes the rough

 ness worse some times. Going from 2k rpms- 3k rpms

 it is almost like it is bogging down, and you have

 to sort of pump the throttle to get the rpms past

 the 3-3.2 k mark.

 

 Doing the mag check it is very rough on each side

 also, and I am using gas with the 10 % methanol(

 exact amount unknown )

 

 My qquestion is any ideas on the cause, there was no

 visible dirt or matter in the bowls either?????

 

 I am going to try and put in new plugs and then try

 some AV gas instead.

 

 Let me know what you think

 Thanks

 Jay


	


 

Want to start your own business?

http://smallbusiness.yahoo.com/r-index

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Nov 08, 2006 12:24 pm Post subject: Rough Running 912 UL

Kurt,



This might be right on the money.  One of the local 912 guys got rid of his 

rough spot by raising the needle one notch.  I followed suit.



Lowell



---

torgemor(at)online.no
Guest

Posted: Wed Nov 08, 2006 12:55 pm Post subject: Rough Running 912 UL

Hi there Jay,



Good description of your rough running engine.



Just change all spark plugs as you suggested, I don't think that you'll  

need to change the fuel, -but it is a good idea.



Methanol/ethanol blended fuel is known to cause starting problems during  

cold season.



The ignition system Ducati is of the type "wasted spark" system, I.E.  

firing twice as often as necessary. However, this is Rotax/Ducati  

philosophy, and work great..



The importance here is that one coil winding is firing two sparkplugs  

(installed in two different cylinders) at same time, one active and the  

other passive (would not ignite anything as this piston is in bottom).  

Over time "one" of the plug "might" become some contaminated (sooty and  

carbonized).



Those two spark plugs can be compared with two resistors. Since one of the  

plugs occasionally can be partly shorted, -most of the spark energy dimish  

and most of the spark energy is transferred to the healthy spark plug.



Occasionally one plug might short and this can vary and play havoc with  

you. 



So, the moral is look at the plug electrode and see if there's one with  

darker color, and if you change this plug you must change the "twin" plug  

going to the other cylinder. I.E. the "twin plug" is the one connected to  

the same coil as the "sooty" one.



But as a rule, we normally change all igniters at the same interval.

P.S. In the ol. days, we leaned the engine on ground for some time -then  

the mag check become ok. and the fun could start.  

Good luck.

Torgeir.



On Wed, 08 Nov 2006 05:02:50 +0100, Jay Fabian  

<experimental208nd(at)comcast.net> wrote:



 	  Quote: 	
		   Hi List,

 I have a 912 UL with 145 tthours. It had a rough spot at about 3000-3200  

 rpms on the ground or in the air.

 I have checked and regapped the plugs to .028,

 cleaned out the bowls on the carbs,

 cleaned off the neddle and dome area, sanded the ground wire lugs for  

 the coils to get a good ground.

 Checked the carb Ballance -its ok.

 It all has not helped at all, even makes the rough ness worse some  

 times. Going from 2k rpms- 3k rpms it is almost like it is bogging down,  

 and you have to sort of pump the throttle to get the rpms past the 3-3.2  

 k mark.



 Doing the mag check it is very rough on each side also, and I am using  

 gas with the 10 % methanol( exact amount unknown )



 My qquestion is any ideas on the cause, there was no visible dirt or  

 matter in the bowls either?????



 I am going to try and put in new plugs and then try some AV gas instead.



 Let me know what you think

 Thanks

 Jay


	


-- 

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

smokey_bear_40220(at)yaho
Guest

Posted: Wed Nov 08, 2006 5:01 pm Post subject: Rough Running 912 UL

Thanks Lowell,



As you know, I don´t have a 912, but lean is lean on

any 4 cycle and I know about sagging power on others. 

My old 2 cycle would run pretty happily rich or lean,

until you fouled a plug or burn a cylinder, but don´t

mess with the timing.  That was touchy.



Kurt S.



Do not archive



--- Lowell Fitt <lcfitt(at)sbcglobal.net> wrote:



 	  Quote: 	
		   Kurt,

 

 This might be right on the money.  One of the local

 912 guys got rid of his 

 rough spot by raising the needle one notch.  I

 followed suit.

 

 Lowell


	


 

Sponsored Link



$200,000 mortgage for $660/mo - 30/15 yr fixed, reduce debt, home equity - 

Click now for info http://yahoo.ratemarketplace.com

experimental208nd(at)comc
Guest

Posted: Wed Nov 08, 2006 6:29 pm Post subject: Rough Running 912 UL

Ok, So far I cleaned out the top diafram area with  carb cleaner, and the needle had a slight dark ring of residue on it on both  pins. 

 Diaphrams are fine, and back in place

 Inlet tubes look fine,

 Carb sockets have about 20 hours on them, and are  clamped correctly,

  

 One thing I noticed when taking off the top cover  of the carbs there is a dark silver  / oil looking residue on the two parts  that hold the big spring in place. I did not know if it is oil for the spring or  just the aluminum rubbing off from the spring. I left it as is for now. Test ran  it and the same issues are happenning.

  

 I ran out of light so I will try the plugs, and the  teflon seat and valves for wear as per the maitenance book.

  

 I know of people that change the jets 2 X per year  depending on temps, but since I built it I have not had to change them at all.  The egts have been great and only fluctuate very little all year round 90deg- 20  deg F.

  

 Where is the middle range system located? Is that  up behind the float valves?

  

 I hope to get over there Thursday  sometime.

 Thanks

 Jay

  

  

 [quote]   ---

propellerdesign(at)tele2.
Guest

Posted: Wed Nov 08, 2006 11:33 pm Post subject: Rough Running 912 UL

If it have that system (I am not sure) there is one  or more extra holes close to the closed throttle valve, clean this and or the  idle jet, and or adjust the idle mixture, because the idle system is working  about one third up in the register.

  

 Se http://www.ultralightnews.ca/rotax912/912-914bingCarb.htm

  

 Jan

  

   Off-idle circuit 

As the throttle is opened up slightly from the fully closed position, the  throttle plate uncovers additional fuel delivery holes behind the throttle plate  where there is a low pressure area created by the throttle plate blocking air  flow; these allow more fuel to flow as well as compensating for the reduced  vacuum that occurs when the throttle is opened, thus smoothing the transition to  metering fuel flow through the regular open throttle circuit.

 [quote]   ---

nandrand(at)xtra.co.nz
Guest

Posted: Thu Nov 09, 2006 12:23 am Post subject: Rough Running 912 UL

It may be a silly question, but have you  balanced the carbs' ??? Noel

 [quote]   ---

experimental208nd(at)comc
Guest

Posted: Thu Nov 09, 2006 1:12 pm Post subject: Rough Running 912 UL

Yes, They are right on the money, with the duel  gauges.

 thanks

 Jay

 [quote]   ---

ppeerenbo(at)charter.net
Guest

Posted: Fri Nov 10, 2006 4:02 pm Post subject: Rough Running 912 UL

Jay I did this to my self by putting a longer tube  on the carb vents. What do your vent tubes look like?

  

 Paul N102DG

 [quote]   ---

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