It is most likely not your oil pump, nor oil in the pump causing this. I had the same thing happen to me, and my kickstarter worked just fine. You don't need to pull the engine and split the case to investigate further, but you may need to, to fix anything wrong. You do need to pull the clutch cover though. Here is a picture of part of the parts fiche. Sorry it is so crappy, but I had to snap a pic of my monitor.
Your problem is most likely with numbers 11,13,14,and 17, maybe even #10, the spindle. #10 is what the kickstarter arm attaches to outside the engine, and #11 is the pawl that engages the starter gear #9. Here are two pages from the shop manual dealing with the kickstarter, as the parts fiche is misleading in that it shows the backside of the mechanism.
Something is preventing the spindle from turning. Could be a piece of crap stuck in the pawl or anything. You are just going to need to check it out further. You said the bike starts and runs just fine with the starter motor. That means the gear turns fine as well, as it drives the oil pump in addition to spinning the crank. Maybe the spindle is broken? I hope it's not #17, as you
will need to split the case for that.
Hope this helps you,
Gonzo
