Cooling Shroud

Category: 2 Stroke Technical Questions 5 months ago

My very used 447 came with a homemade cooling shroud (no fan) that seemed inadequate.  I thought I could do better so I put in a lot of effort and time (and a bit of money, too) and came up with something I thought might work really well.  But then I read somewhere that the cooling air HAS to exit on the carb side.  Guess which side mine exits on -- the exhaust side.  Can anyone explain why it hads to be on the carb side?  

  • Re: Cooling Shroud

    by » 5 months ago

    This is a very good question!

    The exhaust side of the engine is the hottest and must be cooled first. The shroud (from Rotax) not only cools the cylinder head but also the cylinders and is why Rotax makes this statement in the installation manual. I imagine the time and money you spent building and designing your custom shroud would have easily bought the Rotax one. 

    Rotax would not have made the specific statement in the installation manual ("On 2-cylinder-engines the air stream must be directed from the exhaust side towards the carburetor side with suitable ducting") if it wasn't important. 

    Also, don't forget the following statement that's found below the ducting one - "Pusher propeller configurations should not be used with free air-cooled engines without consulting the engine manufacturer (in writing)".

    Keeping your 447 properly cooled is very important! 

    Sorry about your situation; thank you for posting the question and fly safe!

  • Re: Cooling Shroud

    by » 5 months ago

    That makes sense.  For the record, in the LEAF catalog, the Rotax shroud is shown as "no longer available."  

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