First you need to know if the mixture gets too rich, or too lean during warming up.
If it gets too rich, first unscrew the choke-airfilter when the problem starts, with motor running.
Does the engine run better? replace filter.
Not? then check the choke-intaketube that runs to the other side, for fouling/ clogging.
No dirt? you can blow easily through it with a piece of tubing attached?
Unscrew the choke-housing by loosening the two screws,[they're usually very tight] and carefully remove the thinnest spacer that is under it.
This will result in a leaner mixture.[overall].
Mixture too lean; add the thinnest spacer you can buy to the ones under that choke-housing.
Always adjust CO after every change you make on the system.
If my English is bad; I'm trying to do my best as a Dutchman....
Nico
sl restorer, Holland
