There is no site or link. The info has been recounted many times on RCU. Suffice to say that the NC was the most troublesome as it did not have an adjustable idle, only a fixed airbleed which may or may not work for your local conditions. The only fix was re-drilling the hole to a bigger size to lean the idle, a real pain in my opinion.

The FS was the first and most reliable 120 , the SC made monster HP, but was a very limited edition, and the FZ was the last and probably the best from an operational and power standpoint. Then YS dropped it and went to the 140 Sport, which is a bored and stroked 120 in the same case.