Going out on a limb to guess you have the 85 BR. Since that model has a poorly designed fuel enrichment circuit(choke) they are a real bltch to start below 0'c..no matter how cleaned or tuned!!
But that being said, have you checked and cleaned the tank and petcock?? Since a small amount of rust or tank sediment could quickly baff any attempts to clean the carb since this machine lacks a fuel filter. All it has is a screen in the petcock..
Sounds like time for a 'do-over' on the carb work. Secondly there is a choke circuit fix to deal with the cold starting problem..or just message 'FlyingJ' and arrange to send the carb to him for a PROPER rebuild!! Best money I ever spent!!
Then the tank/petcock cleaning with fresh gas..install a small inline fuel filter. Then install another new plug. Any plug that has been fuel soaked will never be right. For $3, replace it..
Do all this and my bet would be you'll never have to screw around with it again!!
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)