It looks like the gear isn't concentric with the center hole.
Give the man a cigar.
Yes this is the primary gear from a Chinese 2 stroke. The engine runs good, very powerful but it has always been noisy and has a strange pulsation and a roughness that wasn't consistant with crankshaft speed but much slower. The gear ratio is something just a little over 4:1, more like 4.3:1 so the pulsations I could feel were more like clutch RPM than crank speed.
Our weather has been so bad that I haven't had a chance to really run this bike much but during another snow storm today I was putzing in the garage and I pulled the gear cover off, pulled the plug out and using a cordless drill with a screwdriver bit, spun the crankshaft. "Holy wobbles, Batman. That little gear is way off center and it wobbles side to side."
Not only is the gear not concentric with the crankshaft but the bore is drilled at an angle. The gear would bind then loosen, bind and loosen as it meshed with the clutch gear and it wobbled. Close examination of the teeth clearly shows the abnormal wear pattern.
My point is that I wonder how many times owners have blamed an out of balance crankshaft on their rough running engines when in fact it might be this gear that is causing their problems.
I'm replacing this gear with a new one tomorrow and I'll report on the results.
Tom