power loss in flight

When I brought S6S, 912ul with Sports Wing it was 6 years old with you 170 hours on it, first time it played up was the 5hour flight home. 

The "similar " problem I had was not every flight but when set up in cruise it would feel like a extreme case of carb ice (maybe only on one carb) or someone rapidly switch on and off the mag switches.
If I yawned the plane and flew crossed controls it would dissappear immediately, so thought it would be in the carbs.

After overhauling the carbs and checking all electrical components it still did it.

Next I added a fuel return line and electric carb heat, still no difference.

Installed a airbox and the problem went away. Removed airbox and the problem came back, airbox back on and no problem since.

I'm pretty sure it was disturbed airflow around the carbs but have only herd of the problem on a couple of S6's

If you are feeling vibrations a higher RPMs, the problem could be the Prop.

A check of the prop balance might be in order.

If you can maintain level flight at 4900 rpm, your plane is either very light or over-powered.  OR ...

It is Over-Propped.

Can your reach 5700+ rpm in a Vy climb at WOT?

Can you reach 5500+ rpm in level flight at WOT?

If the answer is NO to BOTH of these questions, you are over propped and lugging the engine.

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Rotax is Not the source of the Float problem.

The Floats are manufactured and supplied by BING, the maker of the carburetors.

Rotax is just as much a victim as the rest of us.

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Before you go out and spend $300 for a set of floats for no good reason;  Spend $9 for a scale and weight what you have now.

The problem might just lie somewhere else.

Check the Carb vent lines.

https://www.rotax-owner.com/en/videos-topmenu/rotax-minute/454-carb-vent-lines

Thanks again for responses. 

My carb vent lines are 3 in tucked in bowl bale.

As far as cruising below 5000rpm, it’s wonderfully smooth and quiet. Many 912 owners and pilot magazine testers have stated the same. I easily maintain flight at 4800, at 5200 its about 105 mph (I have the speed wing). Have never tried to redline it, I reduce throttle during take off when it gets to 5400, it accelerates unbelievably fast.

Most of the float / carb issues seem to include rough running at other times, which mine doesn’t seem to do.

The airbox appears to address my issue. Am guessing expensive.
and will it always fit ?

Also the weirdness of...why did it not show up in first couple hundred hours ? 
Will be investigating Airbox.

Would like to hear Bings explanation as to why they switched to inferior floats.

I have almost 1400 hrs, this being my 4th aircraft. And have been extremely lucky as to lack of mechanical issues. 
Dang, time to pay the piper I guess.

thx 

hey.

on your Rans with power loss corrected with airbox, did the power loss only occur on hot humid days ?

Or didn't seem to matter ?

thanks Dan