The best suggestion I could give you is to abandon your project. There are no realistic consideratoins in it.
The engines you planned to use are just 10 Hp. These are moped engines and they generate their maixum power at lower RPM's. These engines are designed to operate at ground level, wherein majority part of these engines are run at low RPM's and at fixed Temperature
If the weight of the aircraft is 100Kgs, the propeller needs to displace similar KGs of air than the weight and this propel's the aircraft. To Propel such amount of air, the propellers must be able to rotate at least 1000 RPM, roughly. The engines mentioned can never be able to propel the propeller unless a gearbox is used, which complicates the things.
The pressure exerted on the propeller is huge and you need a short gearbox with short lag. Which means an automatic with less lag. Anything manual with huge gear gap might break the propeller or Engine in an instant.
There are people who mentioned about a Cessna 172. That has over 5000 CC engine which is generating a mere 100-150 HP. What does it tell you? Its a huge engine running at low RPM and generating maximum Torque.
Remember, you cannot rotate the propeller more than 2000 RPM. It breaks the speed of sound and in this process, the propeller itself might break. You need a variable pitch propeller on such small aircraft which might be expensive.
The engines you mentioned cannot operate at an altitude above 3K or 4K easily. They just choke. How do you climb? You need a much bigger engine, which can generate enough thrust.
At Ground Level, you should be able to pump up the weight of the aircraft so, you can fly. But at altitudes above 1000 Ft, the air becomes thinner drastically and your engine needs to propel 2X or 3X or maybe 4X more. Which means, it should do 3X or 4X more work at thin air lacking oxygen. Remember, Oxygen is a heavier gas and concentrates around the ground. The higher you go, the less oxygen is available.
Most of the old aeroplanes used a manual fuel adjuster, wherein the pilot adjusts the amount of fuel pumped into the engine, depending on the oxygen availabilty. With Fixed carb, that's not possible. You would need a Fuel injection.
Temperature above 3K falls by around 40% from ground level. Will the engine break when it experiences such drastic differences in temperature?
There are a hundred other things which I did not mention here which might be fatal.
I am not saying it's not possible to Fly. It's possible, but will you be able to reach your destination? You will be able to fly for a few meters and technically you flew. But is it what you want?
If you really wanna fulfil your dream, look at Diesel engines, Or Rotax engines, if you can procure one. That should solve the problem in an instant. And Regarding Kmpl or MPG, don't expect it to be cheap. If it can be cheap, we would have been flying instead of riding mopeds.
Even if you try to fly with this engine, the minimum speed you might need is around 60 Knots, which is 108KMPH, which this engine can never reach. Possible if you use a 8 speed gear box and even at that speed, the power generated is so minimal to lift the aircraft.