It is a great bike but from personal experience and that of many, many others, stay away from early bikes with an engine number that sits, roughly, in between 6200 and 9500 and generally was made in 2008/9 (mainly 2009). They have a very well recorded (here and in other sources) of fatal engine failure as a result of the 3rd gear disintegrating and massively destroying internals.

The Yamaha 660 engine has been made for many years and is fitted to Aprilia, MZ, and other bikes so the known cases of failure are small compared to the overall number of bikes but definitely are known to fall in the above grouping.

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I have a lot of growing up to do. I realized that the other day inside my fort.