What determines oversized and undersized?
There are standard sizes for the components of a particular engine. I suggest that you download the Repairmans Manual for Briggs and Stratton engines. It has several excellant excellant sections on engine troubleshooting and rebuilding. I will post this and then try to add the link. Tecumseh may have a good manual too. You can download three free manuals per day. Good Luck, Rick
Take some time to read this manual for general knowledge http://gardentractor...pairman-manual/
This manual may be for your specific engine http://gardentractor...hh120-overhaul/ There is a section that shows the standard sizes and specifications of components.
I suggest that if you have never done something like this before find a cheap engine to learn on. I pickup free lawnmowers at the transfer station. They are perfect for learning on.
Edited by boyscout862, September 02, 2013 - 02:52 PM.