I had a cold start problem with my '81 R65, below 55F. the bike was difficult to start, the colder it got the worse the problem became .
I had the second generation red and black OEM ignition coil .
The primary circuit in the coil should have 1.5 ohms, mine had .5 ohms .
Replaced the coil with a Dyna brown coil, now the bike starts with no problem, the coldest I usually see, is upper 20's F.
Now, if ignition is not an issue, what is your starting technique ?
My usual is turn fuel on, get my jacket and gloves on, then full 'Choke', use starter until the engine fires, then add a little throttle, bring the 'Choke' back to the half detent .
Don't hold the throttle open, the bike will rarely if ever start, if you do this on the first 'cold' start of the day .