I picked up a Loncin 90cc (NST Branded) for my daughter and trying to get it up and running.

• New carb w/ factory main jet (tried multiple carbs on hand and all reproduce the same issue. Including known working carbs)
• Adjusted valves
• Has a new wiring harness + cdi + ignition switch + starter relay + kill/start switch

Had to add a new wiring harness as the original was toast.
Got it running initially and went to ride it with myself and daughter on it - not even considering the fact that the tires were completely flat. So it struggled for the 5 ft it drove and then stalled out on us.

Since it stalled out I can't get it to run any longer than a few seconds.

It makes a long hissing / slow release from the exhaust. This takes quite a while and unlike any air exiting an exhaust that I've heard.

At a loss right now.

 

Ended up being a clogged up exhaust.

Pulled it off and it fired right up.
Blew it out with air compressor and now air flows freely. Bolted back up and fires right up.