Hi Corduroy, here is the Illustrated Parts List for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/18muvJXEnfBhU7y.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/msvtJR-K_ny7tH217FzoPu.pdf

As you can see from Page 6 of the IPL, your engine has a pneumatic governor, not a mechanical one. Equally importantly, it has a Governed Idle, so idle speed adjustment is more complicated than on the (mostly older) engines which do not have Governed Idle. Your engine also is a version with a Low Emissions Carburetor. Here are the instructions for setting up the governor mechanism:
[Linked Image]

I suggest you read the instructions carefully - they are rather obscure. Note that the full B&S technical manual for your engine, and all other post-1984 single cylinder side valve Briggs engines, can be downloaded from the manuals area of this site. It is listed as Briggs Part Number 270962.