Not a manual in particular, but this is the Bob Ross of small engine repairs' channel:

https://www.youtube.com/channel/UCr_GXW2Y56hOpGchXYNqZOQ

I learned from another mechanic, no book recommendations, sorry.

R. Bruce Radcliff Small Engines 4th Edition ISBN-13: 978-0826900333, ISBN-10: 082690033X