The 750 rotor shows TDC to be 9-10° different at 345°
This shows the stock kz750 centrifugal advance rotor TDC lines up with the 345° mark showing that the 750 crank and locating pin is indexed 9.5~10° different than the 550.
So a difference in crank stroke between the two motors may be the reason for the TDC index to not match between the two seemingly identical rotors. There is also a .5 of a degree difference in initial timing between the two rotors which would be impossible to see with the naked eye.
But the fact is that the ~10° difference between the rotors means they are not interchangeable between the two engines.
As for how the timing rotor works on the Zephyr's is kind of a mystery. None of the service manuals explain how they work, only how they can be diagnosed/serviced.
On the zx550's with dual pickups and a rotor with one single "bump", each pickup will tigger one coil as the rotor bump passes by. The Ignition module also measures the voltage pulse created by the bump passing by the pickup. The voltage pulse differs with the time it takes for the bump to pass by the pickup, thus giving the ignition module a way to measure the engine RPM's so it can adjust the ignition timing accordingly.
So the zx550 setup is pretty simple. Bump triggers one of the two coils, coil fires on two cylinders (wasting a spark on a cylinder that is on the exhaust stroke) and the pulse is measured to figured out what the rpm's are and adjusts the timing.
The Zephyr has only one pulse pickup and a rotor with four bumps. Which is super confusing to me, so all I can think of is:
So because there is only one pickup module
, I think the smaller bumps are used to tell the ignition module every time a coil needs to fire and which coil it needs to fire. (again...one coil fires two different cylinders at the same time, wasting a spark on a cylinder that is on the compression stroke. Hence the wasted spark name.) And the larger bump serves to trigger a coil and also creates the voltage pulse that the ignition module needs to determine the RPM's. But I don't under stand why there isn't just two bumps 180° opposite from one another used to trigger the coils instead of four. So maybe the smaller bumps create a metronome effect that the ignition module uses to time the firing of the opposite coil 180° after the first one fires. I'm stumped.
Last edited by DaftRusty
on 13 Mar 2018, 19:54, edited 2 times in total.