Your engine is also of the right age to be covered by the B&S engine overhaul manual, which you can access here:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_70.htm
(just increase the "70" at the end to access subsequent pages).
If anyone knows of another site where this manual can be accessed - especially one where it is easier to go from page to page - please let us know.