a friend of mine has an 83 yamaha exciter that looses spark intermitently. It runs like a banshee, but when it warms up ( usually about an hour of riding) It just dies. Has anyone experienced this with a YAMA ?? What was wrong? CDI box? Throttle safety switch? I told him I'd ask here, just incase it's a common yamaha problem. Thanx for any help. It really sux when I have to tow his dead horse down 6 miles of rough trail, just to have it start and run fine the next day!!