We've had this for over three years now:
She's a '97 model. We started off doing loads of trackdays on it for about a year with no problems whatsoever. Then after three days of us both using her at Jerez she started going *rattleRATTLErattle*
Turned out one of the powervalves had broken and fallen into the barrell. Spent near £800 getting her all rebuilt nicely for Couch to race.
He did a season on her with no problems other than a snapped throttle cable
At the end of the year it needed stripping down and checking over and it turned out one of the barrells was a little worn on the exhaust port and the rings had been catching it and slowly taking lumps out! So another £700ish rebuild and she feels SO much better now
Couch has just put it back to a road bike, so I've been out on it terrorising anything and everything
It makes you feel like a racer all the time, everything's a target, every gear change has to be perfect so you don't drop it out the power, slip the clutch out the corners....it's so addictive. I don't think we'll ever sell her, it's one of the most frustrating little bikes in the world some days, but it makes me grin like a loon everytime