Motorcycle Repair: 1983 honda cx650custom, haynes manual, rich mixture

Question
my bike is hard to start, i have to pull the spark plugs out and clean them especially when the bike sits for a few days. they get a black build up on them. hard to keep a idle when i do get it started, but once it is warmed up it is ok. when i reve it up while trying to get a idle it backfires also.
i have replaced these plugs and get the same results

Answer
Mike,
 Sounds like you are running too rich.  Check a good manual for the air/fuel screw setting.  It's possible your carburator needs to be cleaned and adjusted.  A Clymer or Haynes manual will walk you through this.  The backfiring can be caused by improper timing however due to your other ills I'd say it could be from the overly rich mixture making its way into the exhaust before igniting.  When examining carbs. be sure the choke is working properly (fully closing and opening) and that the float level is set correctly.

Hope this helps,
Mike