Hi,
I had the exact same issue after my rebuild, the kick start was stiff and I could hear a slow gearing noise which was the starter turning with.
The reason is the starter freewheel which is locked on the starter primary big gear wheel behind the rotor.
You can check it easily by removing the small starter cover on the left engine side cover. you'll see the starter gearing turmning whick you kick.
I was able to start the bike and unlock it by pressing the starter button while kicking, however after stopping the engine it got stuck again 9 time out of 10.
During the engine rebuild, the freewheel was the only part I hadn't completely disassembled, I cleaned it and washed it many times in fuel but without removing it from the rotor. This was a mistake, it was in fact not deeply clean, the freewheel is very sensitive to any particle or chip.
So I disassembled again the rotor from the crankshaft and removed the frewheel from the back of the rotor. You have to remove the 3 screws which are "punch locked" at their end (don't know thnow the english word for that...
), an impact gun helps here.
The freewheel looked clean but there were some particles and chips locked inside. I cleaned it like a surgery room and reassembled enerything (punch lock the 3screws again). Now everything works again perfectly!
