The Friendship Bike - NobleHops restores a 75 Z1

Did you ever find out why the front cam chain guide snapped clean through ? I have a 75 Z1 900 that has the same issue ... I dropped the pan to clean sludge and screen and found a 2" long piece of the front chain guide in the pan

Same thing happened to me. A 1" piece popped out of the oil drain during an oil change. Went in and fixed it. I am going to guess this is a rare occurrence and is due to the front chain guide having manufacturing flaw. Any manufacturing process can have one or two flawed parts get by, no matter how high the quality. I think this is the exception and not the norm. But for the most part, these Z1 and KZ motors are pretty high quality and pretty bullet proof.

Very common. When the rollers get hard and start coming apart with age and acids in the motor the chain whips on accel and decel causing it to break. The center roller and the chain adjuster roller are "rubberized" and start coming apart. If you find chunks of black plastic in the oil it's time to change them. The Liska's are great but you still have to use the guide and center roller. Thankfully they are cheap compared to the rest of the cam train components.
Steve