What causes backfiring?

[Lindso]

My bike only does it on initial start-up, and only if I try revving it a little. Plus, for the first 5 minutes or so, LOTS of smoke, and if I try giving it even just a little too much gas to get it to roll, it bogs and stalls out. But after it's been idling for 5-10min, it runs like a champ.

I don't wanna blow up the reeds, though I'm sure I'm due for a V-Force. But as is the problem with getting the oil block-off and the larger gas tank, I don't wanna spend $$ on myself til after the holidays. In the meantime, is there some adjusting or fixing I can do to refrain from screwing anything else up?

 

[Wildcard2]

It is a sign of a lean condition, colder engines require more fuel...hence the reason you have a choke. Full choke for initial startup, 1/2 choke during warmup. Make sure your jetting is correct by doing a series of plug chops, as the weather gets colder your bike will need more fuel as well. This is all because cold air is more dense than warm air.