Cold weather screws up engine - carburetor air/fuel or jetting?

[LewieBike]

Back in 2007 I bought a Chinese Lifan 100cc pitbike engine with carb, intake manifold, shifter, kickstarter and CDI for $178 shipped that was grafted into an old Yamaha what I was fixing up.

I put well over 10K miles on that bike before it started running poorly from stretching the cam chain. Otherwise very little problems with it.