the tilting of the bike causes the floats in the carburator to rise wich cuts off the fuel intake
Gravity.
downshift
It requires extra power to go uphill, against the pull of gravity.
Going uphill takes more power than going on the flat, so unless you can add more power, you have to trade some speed for power to be able to go uphill.
check the air intake
Could be a clogged catalytic converter, rotor cap is bad, fuel filter is clogged, fuel pump dying.
Is the vehicles transmission downshifting to a lower gear as you go uphill? If not, that would be your first place to look. After that I would suspect that your engine timing is not autmatically advancing as it should be.
try changing the fuel filter
The parameters for engine cc are the amount of power or torque required for the purpose to befulfilled. Taking example of the motorcycle engines - as the amount of cc in the engine increases, the capacity of the engine to carry the passengers at a faster speed and the ease of going uphill increases.
Have you checked to see if you are leaking any oil while you're traveling uphill? Loss of engine oil will cause your car to lose power, and eventually blow your engine if you don't replenish it. How much power are you losing? Every car will slow down when you're going up a hill and will require you to push harder on the gas to maintain the same speed. A bad knock sensor will cause very weak acceleration. This happened on two of my subarus. It is an easy fix and improves the situation immediately.
Any engine will lose RPM going up a hill, its called gravity and the engine has to overcome it. The heavier the vehicle the more RPM you lose. Thats also why transmissions have all the extra gears. Lower gear equals more pulling power and less speed, higher gear is less pulling power and more speed.
When alot of engine power is needed, the A/C compressor will be shut off to reduce engine load.