The timing can be changed as the outer body {sealed red plastic body "windings"} has three slotted fixing holes, about 15mm of change. the internal rotor is not keyed from new. I have keyed mine due to the fact that I want to be able to add extra weight when I want, this just safe guards me from one of those silly breakdowns at the end of the section?
The internal rotor design of this unit is very different from all others that I could find, also reading reports from gokart and scooter forums on this Brand of unit all reports are of praise. The torque curve I am not sure of, but it seems to be spot on as I have ridden two others that have been changed to electronic ignition and they seem to either rev well or pull down low there was no real comprimise? With the unit fitted there is around 35mm X 135mm of room to fit what ever weight you want {i've fitted 135mm X 17mm bi metal tin/alluminium} and also have made a lighter one from stainless steel.
The unit was bought from Mr Juan Zurera, he can be contacted by email: ossatrebolbcn@hotmail.com.
The system cost 195euro + postage, I am from Australia so there may well be more dealers in US or UK.
Hope this helps...