Hello Thomas,
All things being equal, i.e. good compression; spark at spark plug; speedy engine cranking; petrol and air available in correct strength then the engine should start
However, nothing is ever as it seems on paper
I have found by my own experiences that with a carburettor engine and modern petrol that it is always preferable to switch off the petrol supply and let the engine run until the carburettor is dry
then switch off the ignition. Modern petrol is so much of a mixture of chemicals that the essential ones evaporate very quickly and the residue either corrodes the inner parts of the carburettor and/or fails to ignite during starting.
Might I suggest that you; switch off the petrol tap; drain the carburettor of any 'petrol' it has in 'store'; leave the drain screw loose and then switch on the petrol supply to flow some fresh petrol through; secure the drain screw; lock wire the drain screw so that it can not fall out on the lanes; allow the area to vent and then retry to start.
Normal starting requires the choke when cold and I do not operate the throttle until the engine has fired.
Try this and get back to me with any result.
TTFN
Hugh.
PS Mario - the file is too large as a PDF and I lost the original file trying to make it smaller, will try again later.