Firstly, an admission.
I don't have an XT660, but an MZ Skorpion that uses the XTZ660 engine, so I hope no one minds.
I've joined this forum to understand a bit more about the 5 valve engine and any advantages of the later 4 valve XTX. (Is this the same engine as the MT03, for instance?)
Also, how do I post photos on this forum?
Many thanks
Bill