I know next-to-nothing about small engines. Can anyone recommend a good beginner's book for someone wanting to learn about 4-cycle engines? I have Briggs & Stratton engines in two riding mowers and one push mower.
Thanks.

There is a textbook called 'The Briggs and Stratton Small Engine Textbook' written by Bruce Radcliff, who is the director of education at B&S. This is an excellent book. It walks you through all aspects of engine theory, and operation, both 2 and 4 cycle.

Although a bit pricey brand new(upwards of $100), you can purchase one from Amazon for under $30 when you look at the 'new and used' section.

This gives you underlying operation and prepares you nicely for being able to understand one of their Service Manuals.

If you want to just 'dip your toe in the water' for free, go up to the sticky post at the top of this forum for the link to download a Tecumseh Service Manual.

Keep in mind the Service Manuals are targeted at an audience who already have a baseline familiarity with engines. The book I mention above has great color pictures, diagrams, etc. and makes learning about engines not seem so daunting a task.

I have that book as well as a bunch of others and think it's your best place to start.

Good luck!

Just stick to popular forums.