I recently bought an 850 Roadster that had been idle for 4 years. After about 200 miles it started to smoke badly on the left side only. I figured it had probably lost its valve seal and after much research on the subject found an excellent article on Accessnorton.com (dated 30/8/10 "valve seal replacing". Can't attach it as it is too big) on how to replace seals without removing the head. This is an excellent article and I have just carried out the procedure and found the seal was floating on the valve stem (the seal feels a bit hard and the bottom section that is supposed to grip to valve guide is splayed). I haven't quite completed the job as the rocker shaft is now in the freezer until tomorrow but I'm very optimistic that the smoking will be gone.
Just wanted to share this in case anyone else will find it useful.
David
