Engine will not make power after carb install, post-overhaul

Sorry, one more point.  You say it is a Rotax airbox?  Are you sure that the connections to the carb heat are correct and the butterflies in the airbox are working?  I would also check to see if the vent connections on the box are clear and not plugged.  They need to connect to the upper nipple on the box, the lower is a drain for any accumulation of fluids.  

Cheers

The prop is a two-blade wood sensenich. 

Mr. Rotax wizard,

i thought all intakes were supposed to face forward to have ram air? Please clarify what you mean by "RAM air" as I'm not sure im understanding what you mean. The intake is factory from Tecnam, through a clean air filter mounted in the lower cowling and up through a 2" scat tube into the airbox behind the carburetors. I'm not sure how to re work this without deleting the factory cowling and designing my own intake. If this was an experimental, I for sure could wild west on it and come up with some scrounged together intake, but seeing as its a factory built SLSA, I want to retain the value the my customer currently has in the aircraft.  

As for the induction system being a restriction, We removed the airbox from behind the carburetors and ran the carbs with no induction system, with no change. I'm inclined to believe what's been said about the sensenich wooden props just being pitched for a slower static RPM. 

As long as you have the factory correct air filter you should be OK, it will slow the air and stop and "ram air" effect.  With a CV carburetor the fuel is determined by a slide that has a taper needle into a jet.  The inlet air flow will accelerate inside the venturi of the carb.  The faster the air, which should be determined by the manifold pressure, the more the slide will move up and give you more fuel.  If you RAM air into the venture it will lift the slide, with the needle, an excessively high pressure will give a rich mixture.  The air has to be static air pressure, the same as the altitude density you are operating at.  A false pressure from RAM air will disrupt this and give you a lot of problems. 

I would find out if that prop you have is in fact the stock one supplied from Tecnam.  The real test is in flight at WOT it should not overspeed straight and level.  The target would be 5500 max continuous RPM level flight.  If you are not attaining this it would suggest it is over pitched for the engine.  (or the engine is running at low power for some reason) 

Facing an air pick up forward is not always for ram air, it is normally to get clean unheated air.  Air at the rear of an engine in a cowling tends to be hot, this can cost you power.  Remember how we check carb heat when your aircraft is fitted with a hot air system to melt ice.  When you turn it on at your run up, normally 4000 RPM as in your mag check, the engine will drop RPM.  This is because the hot air has less density, a lack of O2 for each cubic foot of air you suck in, this costs you some power.  Best power is cold, denser, air. 

Knowing it is a Tecnam helps, for sure there are lots flying but not many with a fixed pitch.  Normally they are a ground adjustable and you can match them to get best performance. 

Cheers

Tecnam years ago put on props that only got 5200 rpm WOT in level flight.  Someone that lives at sea level and only flies at 2K ft. will have a different pitch setting vs someone who’s always at 8K - 10k. I’ve changed a few to say the least. (100+) I set all the LSA to get at least 5600-5650 WOT in level flight at your average altitude. (Ground adjustable) If they need a better climb prop then up to 5800 in level flight. This part becomes a personal choice. Yes it would be nice if we all had in flight adjustable props.

As RW stated anything under 5500 rpm WOT is over pitched and stresses the engine plus you lose climb, cruise, fuel economy and cause higher engine temps on climb out.