So I have two QT50s. One of them runs great. The other doesn't run at all.
On the non running one I get the same compression as the running one.
To rule out fuel issues I installed the carb from the running one.
To rule out CDI issues I swapped out the CDI from the running one.
I am getting great big blue spark after I replaced the charge coil on the stator thinking initially that may have been the issue.
I have a brand new battery installed.
Yes I have clean fresh premix fuel. (the oil pump was deleted)
Basically I kick the bike over and at the end of the kick I get a single "pop".
I have even gone as far as removing the exhaust thinking it had a blockage.