Hi there, I just got wind of this thread. I've had a 1992 Gasgas GT-25 (Contact 250) for three years now. You'rs is an extremely clean bike, but the front and rear fenders are not OEM, not that that matters, just so you know (you probably already do). If you run into trouble finding parts I recommend dealing with http://trials.duess....tings/start.cgi these people. They're based in Vancouver, BC Canada, and so far have had everything I've been looking for 'IN STOCK" which was a considerable shock and immense comfort to me.
When I got my bike I gave it a good 'once-over' and got it working properly. Now that it's winter I've stripped it to the frame and am going over the whole works meticulously to get it back to original condition, not for the sake of appearance, but more for perfect rideability/dependability.
The only issues I've run into with this bike is the main nut that holds the clutch on the shaft let go, and trying to find that nut was a thorough nightmare. It's some bizarre thread that I could only find from a vespa shop in Italy. Also, the transmission gear oil needs to be carefully selected. If it's at all too thick the clutch plates will stick and you won't stop when you want to, which is embarrasing when riding behind someone who takes a minute to look around and you run into them. I run ATF now, the manual states 5W30, but I couldn't make it work.
If you haven't found it already, http://www.trialspar...a.com/tech.html this page has all the technical info you should require.
Cheers
JB