Originally Posted by slartidbartfast
How do you know it's lean?
Do you have fuel filters? Could there be some debris in the fuel line, fuel valve or needle valve? Have you blasted carb cleaner through all the carb passages and jets or does it just look clean on the surface? Have you checked for water in the fuel? (drain the carb bowl into a white container and look for beads of water running along the bottom)
Are you sure the spark is ok? If I were to suspect something that seems like lean but isn't, I'd look at that before suspecting timing. Have you checked compression? A sticking valve or broken ring would lead to an air blast sound as air escaped past the bad seal.
The bike will only run when choke is out + massive backfiring, lean for sure. Carb was cleaned and re cleaned every part of it! valves where a tad loose but nothing to cause this. All fuel has been replaced with fresh stuff, there have been some good suggestions on here and I will be working on it more this weekend.