It depends what you want to do, I'm guessing you do not care too much about fuel and combustion research, and more on practical aspects.
Here's some overview references:
https://auto.howstuffworks.com/engine.htm
https://www.howacarworks.com/basics/the-engine
https://www.goodreads.com/book/show/255807.Internal_Combusti...
Perhaps the most interesting thing with motorcycle engines is the variation of stroke and bore and number of cylinders since it's an exercise in packaging and weight reduction to fit on the smaller frame.
In terms of engine technologies different fuel injection strategies and cylinder geometries are areas of active research, along with things like lubricants and bearing surfaces etc.
The 'computational' pieces are really edging towards applied chemistry in figuring out how to optimize the combustion chamber.
For practical tasks without a machine shop you are fairly limited - I would caution against mucking about with an actual engine you later want to ride, beyond hobbyist level until you have some experience.
At hobbyist level it's really about engine mapping and upgrading the air intake. Those things are the easiest 'mods' but I'm sure specific forums for your motorcycle will be able to point you towards common upgrades etc. and why they work.