About a month ago--I shared the story of losing 39 teeth out of 45 on the rear Al sprocket of my 929. I replaced the rear sprocket thinking that the steel front could go another 5K--8K on last 520ERV2, AFAM sprocket kit
WRONG---
I replaced the chain, and just for kicks checked out the front sprocket. although its steel, it had some gnarly tooth wear, ie they were thin, and hooked--replaced everything---I was surprised that the steel had approx the same life span as the Al---granted this is all 520 lightweight shit---BUT it is definitely worth checking out the countershaft sprocket---if in doubt