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Hello group, I’m an A&P who is fairly new to working on Rotax ( I passed line and maintenance courses last fall) and my current gremlin is a Tecnam P2002 Sierra, flying a 912ULS. Customer just got his carbs redone with motive aero. After carburetor install with new crush washers on the fuel feed lines, we balanced the carbs nicely, but the problem is that the engine won’t make full static. 
The carburetors are both at full open stop and the throttle cables are slacked, but engine speed never advances past 4800, stabilizing around 4750-4780. Previous engine runs before pulling the carbs yielded no issues, everything in the right ranges. 

I called Motive and they said to do a compression check and inspect a few things, but in my mind either I’m doing everything wrong here or there’s something up with these overhauled carburetors. 
I need someone smarter than myself here. Thank you. 

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

    by » 4 weeks ago


    Sounds a bit like a prop pitch issue - you sure it hasn't been worked on?


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

    by » 4 weeks ago


    Prop has not changed. The previous owner had installed some “manual mixture” where they drilled fittings into the tops of the carbs to manually regulate them I guess…the carb overhaul was to put un-molested chamber tops on and freshen up the carbs. He’s in an S-LSA so he wanted to make sure it was fully legal. Before this, engine spun fast enough and make power. 


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

    by » 4 weeks ago


    I am no expert Connor - as a general rule there is only four ways to prevent an aircraft engine achieving its full potential rpm:

    # Propeller pitch

    Air restricted

    # Fuel restricted

    # Exhaust restriction

    If the prop pitch is correct, I would look at both fuel and air in exhaust out restrictions.

    Has your carburettor fuel metering been changed (position of the circlip on the needle)?

    Is the carburettor being starved of fuel - float bowl float height, fuel line or filter blockage, pump working as it should, fuel return restrictor jet missing ?

    Is your air filter partially blocked?

    Has an exhaust silencer baffle collapsed? Check for free flow.


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

    by » 4 weeks ago


    I did not do the rebuild, or else I'd be tearing back into them...this isn't my aircraft and I'm not technically rated for heavy yet (despite the simplicity of these Bings...), so my hands are tied with trusting the shop did them correctly. I've chatted with them and they've agreed to take them back if we don't find anything else wrong. 

    The owner says that fuel pressure and flow seems OK, but we've got another evening scheduled to start to poke at things and see what changes...

    Would the float bowl vent lines be an issue here? I've been reading every forum I can regarding loss of power and this seems like a common easy fix. 

    The owner is pretty amicable for now, but I have the feeling if I can't find the issue in a reasonable amount of time things can turn sour and I'm trying to keep a customer if possible. 


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

    by » 4 weeks ago


    If everything else looks right, for now I would trust the carbs and at least start by taking a look at the pitch on the prop, especially if the previous carb configuration was "non standard".


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