Kamware The "TopSpeed Motorcycle Performance Calculator" Software  is what I use for calculating engine displacemnt from a particular bore and stroke.  Saves the Pi r squared times stroke calculation and will help you figure out thje displacement from a particular "big bore" kit or oversize piston.  The description states "f you want to calculate the top speed of your motorcycle in any gear, calculate lobe centers, calculate changes in compression ratio after changing bore and/or stroke, this program may be for you. If you want to design a 4 stroke exhaust system or calculate the power of your engine, this program may be for you." Reading Spark Plugs. You pull your spark plug to check condition and whether your jetting is correct after installing that performace part. This page offers a good pictorial display of what you're looking at and what it means. MacDizzy Two stroke tuning. A wealth of information on two stroke tuning Gordon Jennings archive  Gordon was a tuner in the 60's that had a lot to do with quantifying the effects of various changes to two stroke motors.  Whilke it's old, it's definitely worth a read to ubderstand the factors in getting the most out of a two stroke motor. Mota 2 stroke software  Free expansion chamber design software and other useful utilites in tuning two stroke motors. Honda common service manual  Part 1 and part 2 of the 1988 edition can be downloaded from this site. For any model scooter, it gives a lot of information about how each part of the scooter functions. Also many  bits of information not found in the service manual for specific scooters like how to fit new piston rings and how the automatic clutch works.  If you want to troubleshoot a problem, this book will give you the basics about how and why each part functions.