I noticed that Yamaha has a 10v 500cc twin snomobile engine that falls 
into the "80hp class".  I presume that's based on the YZ250F MX 
engine and is called the Phazer RTX

Engine Brand Name	 Genesis
Engine Type	 Parallel Twin
Cylinders	 2
Engine Stroke	 4-Stroke
Horsepower (bhp/kW)	 80 / 59.7
Horsepower RPM	 11000
Cooling	 Liquid
Valves	 10
Valves Per Cylinder	 5
Valve Configuration	 OHV
Bore (mm/in)	 77 / 3.03
Stroke (mm/in)	 53.6 / 2.11
Displacement (cc/ci)	 499 / 30.4
Starter	 Electric
Fuel Requirements	 Regular
Emissions Standards	 Standard Emissions
Fuel Type	 Gas
Carburetion Brand	 Keihin
Fuel Injector	 Yes
Fuel Injector Size (mm)	 43

Looking at a parts fiche I see that's a 180 degree plain bearing crank, 
and not the pressed up MX crank.  It appears to run one balance shaft. 
It does have an assortment of isolation mounts.  The chain is on one 
end.  I wonder if Yamaha will leverage that into a 650 that they could 
pitch against the 650 Ninja and SV650?