@runes Sounds to me that the mixer screw is the problem, as the mixture is wrong. It's either rusted or been abused and consequently the engines fuel/air mixture is wrong. If the plug is getting wet, surely that's from over fueling and the engine running too rich? Which would cause the starting problem you are experiencing.
I would get a new mixer screw fitted before doing anything else, so that you can adjust the mixture correctly and hopefully that should solve your problem. Then that way you will know for-sure if the engine's mix is correct and eliminate that from your suspected fault list before throwing a ton of cash on it. What RPM does the bike idle at???