Motor is hard to start after warm up

Sorry, I thought (Eh-hem, assumed) it was a eletric choke carb. Try to close the choke a tad and the start it up.
If it fails after a try or two, pump it with a little gas to feed it and try again.
It will probably start with the choke closed a little.
The idea being to speed up the air and get a better air fuel mix going.
To much cold air and the engine will not start.