start and idle problems 04 rancher at

I've always hard problems starting my 04 rancher, had a 96 300 and never had problems.
It wont start even on summer Ark days with out choking, then I have to keep the air mix turned up for a long time then after 20 or 30 min of riding, I have to turn the air mix down.

This winter I am having to prime it just to get it to crank even choked and once it is warm, it does the same as above.

Any ideas, I have always used stabil when it is going to set. I have drained the tank, flushed fresh gas through the carb, even changed to the "7" cold weather plug and it still runs the same.

Thanks for the info.