Need help with rotor phasing

Downsr..... may I ask if the kickback occurs immediately when you start cranking, or at some random time after you have started cranking, or when you let off the key and stop cranking? And what ignition system did you have in there before?

In reading your descriptions of how you have checked this, it sounds like the rotor is about 14 or 15 degrees of crank rotation past the center of the desired spark post and heading towards the next cylinder's post in order when it fires. And while I agree that rotor phasing is not a normal cause of starting kickback, let's all remember that this is an MSD and at low RPM's will generate several sparks in succession. The lower the RPM, the more successive sparks will be created. Per MSD instructions sheets, these sparks supposedly last for 20 degrees of crank rotation. So in Downsr's case, the last spark will come at around 35 degrees of crank rotation of the rotor past the center of the correct spark tower.

So with that late rotor phasing, there is indeed some possibility of a later spark occasionally jumping to the next cylinder in order, which may fire that next cylinder's charge. That next cylinder won't be up on the compression stroke by the time that last spark in the spark train comes along but it will fire what charge is in there. That might cause mild kickback, as part of the expanding burnt charge will be trapped in that next cylinder as it tries to come up on the compression stroke. It would also spit back through the carb.

This may also explain the observation of the spark pits on the tower contacts all being towards the 'late' side of the contact; IMHO, this is a valid observation in this particular case.

The suggestion to modify the rotor mounting or cap mounting for better alignment and run it like that for a while, are the best suggestions to confirm or deny that this is the problem. If you retard the timing, it may or may not solve the issue unless you know it back at least 10 degrees IMHO.