I have possibly found a way to avoid carb iceing/poor running in the winter.
For 8 years i have been fighting with this very problem and it has driven me to the point of burning my bike in a quiet field
,I have tried new plugs new HT leads, PRO FST, running the bike for up to an hour before i set for work,I have moved the carb heater sensor to the front of the bike so its not next to the engine,But in one of them EUREKA moments
while servicing said bike i thought i would try to displace the flow of air around the front cylinder.
I got some sheet stainless steel and cut a shield that runs along the front of the engine and blocks any air from going between the front cylinder and the bottom of the radiator the shield overlaps the RAD by half an inch and the same on the front cylinder and runs the full width of the engine and fixes to the lower fixing point of the RAD on the off side of the bike,as yet i have had not overheating problems and i have been running the bike now with the shield for 8 weeks on my 50 mile trip to work in temperaturs of a recorded -5 without the wind chill factor taken into account and the bike is running like new no coughs no sluttering no nothing i will try to put some photos of what i have done on the forum over the weekend.Give it a try if you have the same issues it worked for me.
