I tried to start it with the choke maxed out, (blocking as much air as possible)
The float is empty and floats as it’s supposed to
I do not not what a priming plunger is, could you try to explain what it is, what it does, and how I use it?
I use 95 petrol mixed with two stroke oil for dirtbikes. The ratio might be around 24-16:1 as I didn’t have a milliliter measure around.
The temperature is around 5 degrees Celsius, so it’s pretty cold.
I have pushed the prime sometimes before starting so the carb is full of fuel.
The primer is the little spring loaded thing next to the idle set screw it pushes down on the float allowing more fuel to enter the bowl,.
was there any carbon on the base of the spark plug after your starting test.
If it refuses to start with choke closed try opening a little at a time until full open.
Open the throttle when the engine begins firing.
Do you have access to a compression gauge, for measuring engine compression at the spark plug hole.
I am finding it hard to believe you can pedal the bike from a start, if the engine has the recommended compression (above 120 pounds per square inch), unless your engine is running at idle speed and not responding to throttle.
This is beginning to sound like a problem in the carburetor (maybe a partially plugged main jet).
Myself I never use the primer, or the choke most of the time, but I have an electric motor to help me get up to speed. You can see me start my engine for the first time in 5 degree weather in my video using about 1 third open throttle, you can hear the click where I pop the clutch and see how long it takes for the engine begin to develop full power.