Check the fuel filter and clean the carb, clean the air filter often and service air filter with approved air filter oil. If you\´ve done all that, I\´d get it in for service and troubleshooting. You might have gotten contaminated gas, or your carb settings may need adjusted. Might have defective carb... who knows? My bike has set for a week at a time and she sparks right up. RE: cold weather starting, your issues may intensify, heres my cold weather experience....
I bought my bike in Jan 2006, I discovered immediately in cold weather it is a little more difficult to start, but she cranks up. Even the Service Mgr. was aware that this engine is a little cold blooded. I start the bike with full choke. The bike is a little cold blooded in winter, allow ample time after starting, let the engine warm. 
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