On Monday morning at 0545 (Ugh!)I went out to the bike, which I had failed to cover, brushed the four inches of freezing cold snow off it and surprise surprise had a bit of bother starting it.

Turned off the light to give battery best chance, choked and cranked, no way was that going to start but I got two "rifle shot" backfires that woke up a thousand seagulls and several neighbors. I took the keys out and went in to see if I could find some miracle in an aerosol can, When I returned I could not even turn the barrel lock despite a good greasin a couple of days ago. Not happy! changed out of my bike gear, made a call for a lift in to work and ten mins later I gave it one last try and she starts, sweet as a nut, just as my lift arrives. I did get to work on two wheels but what puzzles me is this. Normally a backfire is unburnt fuel catching in the exhaust sytem but my exhaust was icy cold so where did the ignition energy come from, if it was the plugs why a backfire, why not a start, could I have a valve problem here? once started, no problem and by the way it's last thing at night now and I've used the cover tonight in hope of an uneventful Tuesday morning.

Ok, here it is, Forsome reason cold takes a battery down, not that its Faulty its a thermal chemical type......thing.  anyway, while your cranking its not putting out everything it should, like with cars, the starter will take all the voltage and amps it can, leaving little for ignition. Ill lay odds that the backfires came when just as the button was released and the volts spiked back up while engine was still spinning alittle, one plug would fire and lite off the built up fuel in the pipe.  when it gets cold down here in fla, we have the same issues as the heat and humidity beat hell outa our batteries year round they cant cope with cold snap. now, your gonna laugh, but during a 3 week coldsnap ive put a 60W lightbulb under the engine of my bike and it produced enough heat over night that starting the next morning wasnt a problem.

Yup! I'll buy that Blue, This morning, having covered the bike, no snow but still about -4C started first touch so I'll use the cover when cold threatens and leave well alone, cheers.

my bike doesn't like to start below 20*F
and yes i ride when its that cold

Quote from: Blueknytwhile you're cranking it's not putting out everything it should, like with cars; the starter will take all the voltage and amps it can, leaving little for ignition. Ill lay odds that the backfires came when just as the button was released and the volts spiked back up while engine was still spinning alittle, one plug would fire and lite off the built up fuel

I've had exactly this experience, both good (starting) and bad (backfire):  I'll press the starter, and the bike chugs over, over, over, over, over... and I give up and release the starter button, then suddenly the bike either starts or backfires.  I have held the starter button for 10 seconds without a single "pop", but then as soon as I let go of the starter button, VROOM.  

I agree with Blueknyt: when the weather is cold enough, and the battery marginal, the spark is insufficient to ignite the fuel.  Since figuring this out, I don't bother holding the starter so long:  if it doesn't fire in 3 seconds, I give up and give it a 15-second break, then try again.  After a few failed attempts, taking a 5 minute break to take out the garbage will also help.

Also, I have a can of ether sitting in the garden near the street, for those "must get to work NOW" kinds of days (propane works well too).