I'm doing this route in 5 weeks time, but not on a C90!
As I only have 10 day window I'm going the quickest route, down to Ancona, overnight ferry to Igoumenitsa in north west Greece. Which means I'll be in Greece in 48 hours. Then a 2 day trip to Istanbul. Retuning via Izmir and Athens.
If you take the more direct overland route, you should have an amazing trip. Maybe head for the Adriatic coast and keep going south.
Last year I rode through Czech Rep, Slovakia, Slovenia, Croatia, Montenegro, and had a great trip and found travelling alone on a bike makes you more accessible to friendly local contact.
I have the luxury of lockable panniers which you probably wont, so if you park up and go for a walk around, your stuff will be slightly more visible/vulnerable, but as with most things, the fear of theft is probably greater than the chance of it happening.
As for personal security, I've got myself a discrete money belt and a cheap Casio watch so I don't make myself too much of a target.
Have a great trip and keep us posted