It could be carb icing choking it out. Does it have the stock air box? The stock air box can pre-warm air to reduce the chance of icing.

I have a Stihl chainsaw arctic model that has a heated carb to prevent this problem. Common problem in aircraft. When the temp/humidity is right.

Just thought I would throw this out.

https://en.wikipedia.org/wiki/Carburetor_icing