Cold Starting Issues

So i have an 84 Zn1300 and it does not want to start when the temp is below 70-75 degrees out.
let me step back a bit... purchased the bike about a year ago. guy said it had sat for about 6 months before i got it. then it started snowing 2 weeks after i got it so i sat for another 5 months. Changed the oil, the battery, replaced the front master cylinder....
it had problems firing up and running in the morning (50-60 degrees) but in the afternoon i could get it fired up and run it for a couple of days...put about 300 miles on it. then snow returned and it sat for 2 weeks... wouldnt start, not even crank. was told the battery was bad, so replaced the battery again. and replaced the spark plugs as well as all the fuel lines, thinking the dry rot was the cause of the issue. again would not start in low temps.
so right now i have a bike that will crank, but not start cold or hot without being at full throttle and still will not start in temps below 75.
kind of at a loss ... any help would be awesome.

thanks

-wererat

If you've got a good trickle charger and keep your battery topped up, you shouldn't really be having to buy a new battery all the time.

There's a multitude of suggestions that would help your situation. Since the cold weather is affecting you, I first look at the carbs and a/f screws to see if they're set too lean. Otherwise, where you start depends on the condition of your bike. Peruse the forum a while it's been discussed often at great length if you need more than what I'm suggesting below.

My suggestions on the hard starting:
1) Ignition system gone through: Better coils with removed ballast resistor (stock ones just dont cut it, even when new). New leads, plugs, connectors.
2) Thoroughly cleaned starter motor. The more efficient your starter, the more power you get to your plugs.
3) All connections checked and re-soldered if needed.
4) Clean the carbs, set idle screws set at 3-4 turns out (manual is wrong on idle setting, trust us on that one), sync the carbs. Then fine tune them if you can.

All of this is cheap to do and primarily just requires time investment to do the cleaning, rewiring and adjusting. Made a huge difference for me.