I was given this quad as a project for my son's FFA SAE project and it is in pretty rough shape. He started the teardown and I started trying to identify it for parts. I have tried the vin (CHZZ150R0404DK116) and Google image search and have come up empty. The engine looks like a GY6 with a cvt and says "Thunder" on the cover but no markings on the plastics.

 

The VIN dates it as a 2004 machine. Thunder seems to be a popular name with Chinese makers as there is a Thunder brand, but seems to date from much later than 04. I assume you know the difference between the 4 stroke GY6 and the 2 stroke Minarelli engine, as it could be either from the pictures, both were more popular with makers 15 to 20 years ago, than they are now.