Your engine was made on 7 August, 2003. I have no listing for a Plant 56, which may mean your engine was a very early specimen from the Chongqing plant. If so, that would not be a good thing.

Here is the Illustrated Parts List for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/18hruJXHnfBhU7y.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/29lpAFKT9FzXFix2.pdf

Here is the illustration from the workshop manual showing your governor:
[Linked Image]

It looks to me as if your governor spring is missing.