https://www.ebay.com/itm/A12-Camshaf...1alXGR&vxp=mtr
The above link illustrates the 150cc cam sprocket. Believe you'll find the teeth on it, are like the more pointed ones on the crankshaft sprocket (outer ones).
As far as the missing, backfire, etc....sounds like intermittent electrical problem. Have you looked at the spark plug wire and tightness of the boot. Might even unscrew the boot, snip 1/4" off the wire, and screw the boot back on nice and tight.
It could be something else altogether.....just think I'd check a bunch of other things for misfire/backfire condition, before splitting the case.