You might get better responses to your particular situation in the motorcycle forum.
That will be frequented by folks with first person experience with WI in your application.
That said most of the WI info is pretty universal and the guidelines for water injection rates etc. are posted here in several of the discussion threads. You will find most folks use a rule of thumb of somewhere in the neighborhood of 10% -15% of your fuel flow rate as a starting point.
Take a bit of time and browse through the technical forums and you will find a couple days worth of very useful reading on problems folks have faced, and what has worked and not worked in various applications.
Jet (nozzle) sizing depends on lots of things like your system pressure, how you set the system up, (single jet or multiple jet),
how the system is triggered, how hard you will be pushing things etc.
You will need to consider how hard you are pushing your engine to get a feel for when and how much injection to use.
This website has a lot of good info on motorcycle applications and they certainly have the experience with it to answer any specific questions that apply only to motorcycles.
http://www.rbracing-rsr.com/waterinjection.html
Larry