Paul,

Could a single rotor engine with 80 hp and weight under 100 lb be put
together from existing pieces?  John Uptigrove, who builds the Mosquito
Helicopter
http://www.innovator.mosquito.net.nz/mbbs2/specs.asp
was going to upgrade his ship by installing the AeroTwin engine
http://aerotwinmotors.com/07/pages/features.htm
Apparently the thing shook so bad that his hand on the collective went numb.
He took it out and sent the thing back because he was afraid it would damage
his aircraft.  The engine he's currently running is the Compact Radial MZ
202: http://www.compactradialengines.com/spmz202.html .

I think the single rotor would work well.  The shaft speed of the MZ 202 is
5800 rpm so no changes should be needed in the transmission.  What do you
think?  The Mosquito XE is a great flying little ship according to
everything I can find out about it, it deserves a better engine.

Steve


Not really. Your best bet is a Rotamax if Eric gets it together.
http://www.rotamax.net/  75 HP at 90 pounds.

BTW that is a real cool helicopter. I saw a demo at OSH.
Excellent design. I was mightily impressed.