Motorcycle Questions? Ask a Mechanic.
Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, oil (if not excessive) is to be expected as there is a vent tube from the engine internal to the airbox.
For the "...Runs bad, backfires through the carb...", proposed preliminary tries (if have not been done):
Please post back results / observations of the above once tried.
Appreciate the additional information.
And the voltage check please? ...fuel quality, quantity and delivery?
Appreciate the post back and would look forward to an update when able.