Can I use motorcycle engine in aircraft I am trying to build an Aircraft, The weight of the Airplane will be around 40 Kg with engine and 8 liters of fuel and with me the total weight will be around 90 to 100 kg and I want to use a motorcycle engine in the aircraft, the aircraft will be one seater and I have a question that which type of engine is best to use,

Displacement    123 cc
Engine Type 4 Stroke, Air-Cooled, SOHC
Max Power   10.7 bhp @ 7500 rpm
Max Torque  10.40 Nm @ 6500 rpm


The engine produces a maximum peak output power of 11.00 HP (8.0 kW) @ 9000 RPM and a maximum torque of 9.80 Nm (1.0 kgf-m or 7.2 ft. lbs) @ 7000 RPM

So should I use 1070 or 1065 size wood propeller and if this size is not suitable so please recommend me the best size, 

If this plane successfully flies so what would be speed of it and will it give me same mileage as the engine gives in Motorcycle? And for how long I can fly nonstop with these engines, 

Mine Airplane design would be like this



Please explain me as simple as possible, and Sorry for Bad English. thanks
You will need a fixed landing gear and a braced wing to keep your mass at your target of 40 kg. Expect a maximum L/D of not more than 10, maybe even 8.

You say that the flight mass will be 100 kg. The weight will be 980 N. 1/10 of that is 98 N. To arrive at a power from that will need a few more heroic assumptions. Your wing loading is probably 12 to 15 kg/m² and your lift coefficient around 1.0. This equates to a flight speed of 15.5 m/s (= 56 km/h). I assume a propeller efficiency of 70%, so your power for straight flight will be 2.2 kW.

For decent take-off performance, add 1.5 m/s climb capability at an air density of 1.1 kg/m³. The extra power to climb with those 1.5 m/s at 15.5 m/s and 70% efficiency is another 2.2 kW.

The sum is 4.4 kW which is 5.9 HP. Running the engine at this power level means 54% of maximum power. Make sure you have a gearbox which reduces prop RPM to not more than 2000 in order to make those 70% realistic. The wing will need to have about 8 m² area and the tail another 1.6 m². Will that all fit within your 40 kg?

I expect that 80 kg is a more realistic empty mass. Now the wing will measure 11 m² and the power demand climbs to 3 kW for level flight and an extra 3 kW for climb. Total power will be 8 HP or 75% of maximum power. Ask yourself how long the engine does this and how big your radiator needs to be in order to avoid overheating.