Dear friends,


My engine, a Rotax 912 ULS, has started running roughly on each mag.


Aircraft; UFM-13 'Lambada'. Year of Construction; 2006. Total hours; 530.


Previously it would always drop approx 150-180 RPM on each mag. Now, however, it's dropping over 500 RPM on each mag and running roughly with considerable shaking and roughness. It runs normally on both mags. 




Spark plugs seem unlikely as they only have 29 hours on them since being gapped and fitted last year. I changed the fuel to fresh, quality fuel and that didn't' change anything. 

There's a lot of gents on here posting about the CDI modules giving trouble. It's €400 to overhaul each one at Carmo, Netherlands if I have read correctly. 


If anyone might be able to offer some advice which might see me resolve this less expensively I'd be very happy to hear from you:chuffed:


Kind regards,



PS: Is there any risk of the spark plugs failing to spark when I'm flying?

I have been advised that the design of the ignition system offers the same level of redundancy of a classic magneto (whereby the spark will still be supplied to the plugs regardless of any ignition and/or battery problem) and therefore my CDI problem is only a startup problem -is this in fact the case?





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