Welcome to the Rotax Engine Forum!  We invite our members with Rotax engines, and those with interest in Rotax engines, to post their questions, problems, and successes here.  For "official" support, information, etc., contact Rotax at Rotax-Owner.com.



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Hello John, I will try again, as an owner of a Rotax ULS I have been concerned regarding the plight of a fellow Rotax engine owner who has a ULS in his aircraft,  he recently had the engine seize on downwind to landing and he had to replace the short block . After getting it together when he move the throttle control to idle the engine stops. Can you think of anything that would cause that?

 Thank you 



It may be as simple as going through a complete carb synchronization procedure. There are several videos about this on the Rotax owners forum.


Thanks Bill.

Im hopefully placing an order this week for a 750 Cruzer. Is anyone flying a 750 Cruzer with a 912 100hp carb engine ? Some people are saying it will be very under powered (mainly the people who have used other engines) I don’t have an option to use another engine so it will mean me buying a different aircraft, someone with actual experience would be great.




Well from my experience a 912 uls is not under powered on the CH 750, or my friends Sport Cruser, remember the 912 ULS is also a lot lighter than most other engines.


Thanks Bill

Hi Darren,

I agree with Bill. For you, I think you will find the 100 hp Rotax more than adequate in the power department. I have the fuel injected 912iS in my CH750 STOL. It is definitely not overpowered for my situation because I am at 3000' msl and many of the local airfields are at 4000 ft msl. The high density altitude combined with my plane being quite heavy has me occasionally wishing for a bit more power such as when I have a passenger or am flying around in the Canadian Rocky Mountains. The good news is that engine is very reliable and user friendly. I appreciate never having to add oil nor clean oil off the belly of my plane.

For your location with the lower elevations, a Cruzer with a 100 hp Rotax would be a sweet flying airplane. You will, however, want to build it light in order to retain the advantages of the Rotax's light weight.

Good luck on making your choice.


I received my FWF yesterday afternoon. I started with the engine mount to firewall. This took most of  the day. I got it fitted well and took it off the firewall and painted it tonight. Tomorrow we put ring mount on Rotax 912ULS and if time allows we will start on the oil can stand and bracket. I removed a Jabiru 2200 from this 701. I needed more power at 5000 msl.

I did the first start up of my Rotax 912 ULS. Its quiet and seems to be very powerful. I will need to improve my brakes. at 2600 rpm the plane starts to over ride the brakes. looking forward for the first flight. I will fit the cowl first then go fly. If all goes well I will paint the cowl soon after. 33 days to put it all together/ life and work get in the way.

Rotax 912ULS with 912UL crank and crankcase. What are the PROs and CONs? I can purchase a 912ULS that has been rebuilt with a 912UL crank and crankcase. What would be any issues?


CH701 scratch building

Not sure if this is the correct forum to ask this question. sorry in advance..

Hi Keith and welcome! You're certainly in the correct forum, but likely you'll get more attention/responses if you post your question as a new, separate discussion topic rather than a reply to this thread.  Just go up to the top-right of this discussion and you'll see a box with "+Add."  Click on that and choose to start a new discussion and then choose that and fill-in a title and the remainder of the question/information desired in the dialog box.


Zenith.aero Forum Moderator


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