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Rotax 912ULS

PostPosted: Sat Jun 13, 2009 7:14 pm
by Roger
Has anybody had any problems with a high speed miss on their Rotax 912's?  When I run up to around 4-5000 RPM I seem to be hearing a miss every once and a while. Wondered if anyone else has run into that problem. I'm ready to call the DAR, but not sure I want to before I find out more about the problem.
Any thoughts would be appreciated.


PostPosted: Sat Jun 13, 2009 9:02 pm
by stede52
I haven't had any missing issues with my 912. I wouldn't hold up DAR inspection for that, an issue like that has nothing to do with what the DAR looks at.


PostPosted: Sat Jun 13, 2009 9:13 pm
by scubarider2
No problem with any missing with my 912uls.  I would think there are several reasons that might be causing something like that.  I am no mechanic, but I first would suggest changing plugs, checking wires, checking electrical, etc.  Just my thought....

PostPosted: Sun Jun 14, 2009 9:55 am
by Lynng
I would suspect the carbs are not balanced at the high range. This can be caused by slight cable tension at different throttle positions. Also check your right crab to be sure that the throttle cable end is not hitting the fuel lines running up to you fuel pump which can interfere with your throttle throw. If the carbs are out of sink with each other the resulting engine vibration can shake the fuel out of the float periodically.


912 Rotax

PostPosted: Mon Jun 15, 2009 9:44 am
by Roger
Thanks Lynn, Dennis, and others:
Lynn, did you balance your carbs at idle with the vaccum guages, or did you use some other method?

PostPosted: Mon Jun 15, 2009 9:59 am
by scubarider2
I balanced mine using the gauges I bought from Aircraft Spruce for the Rotax 912uls.  They work great.  Easy to do with TWO people.  One holding the gauges and one inside the plane.  I also viewed the How To video on the Rotax Owner website.  I also have the Rotax installation video I bought that was a great help in setting up the engine in the plane.  

PostPosted: Tue Jun 16, 2009 7:19 pm
by Lynng
I balanced my carbs at idle and also checked how well they stayed together thru 4500 rpm. CHOCK the airplane or tie it down and use 2 people.

Lynn :D

PostPosted: Wed Jun 17, 2009 8:18 am
by Av8r3400
Closely inspect the braided-steel covered leads coming from the stator area (pickup coils) to the CDI boxes.  These can fray and short to the motor mount, or pull loose on one or both ends under torque (higher power setting).  They need some slack to allow for motor movement on the mount.

Had that problem with a 912UL.

Rotax 912 ULS

PostPosted: Wed Jun 17, 2009 7:22 pm
by Roger
Thanks to all:

Soft Start Module for 912

PostPosted: Thu Jun 18, 2009 11:51 am
by stede52
Does anyone have any experience with this soft start module from Bully for the 912/914?  Suppose to eliminate kick back during startup.


PostPosted: Thu Jun 18, 2009 9:27 pm
by b1x4nqb

There was a discussion on this just a couple of weeks ago.  There is also a video on the R.O.A.N. website.  I'm not aware of anyone using one as of yet.

Paul, PA

PostPosted: Fri Jun 19, 2009 12:38 am
by stede52
thanks Paul, I missed that discussion


Re: Rotax 912ULS

PostPosted: Thu Feb 18, 2010 10:34 am
by fly away
Hi Roger is a German producer of synchronizers. He sells its products all over the world.
I think he is the only one who can offer the tester with a Capsule pressure gauge and Zero adjustment.
Scale range from 0....600 mbar; equal 0...17.7 mercury vacuum. A dampening system will avoid vibration of the needle.
There you get a lot of informations about synchronizing carbs.

Re: Rotax 912ULS

PostPosted: Thu Aug 12, 2010 2:39 pm
by oltmr
I have an SLSA. My maintenence manual refers to the Rotax manual for maintenence. The Rotax manual requires factory training to perform any maintenence on this engine. It also requires the engine be overhauled at 2000hrs OR 10 YEARS. It appears that by including the Rotax manual in this manner these requirements become mandatory. I cannot find any Factory trained mechanics in my area. I find A&P mechanics that think they can do my annual conformity inspection but it appears they are mistaken. Worse yet, I don't know any recreational pilots that fly more than about 50 hrs per year. At that rate the overhaul will be due at about 500 hrs. This makes the overhaul allowance in excess of $30 per hour. This is outrageous. has anybody else run into this?