hi, the most common problem in our area for fires on 9000,10,50,60 conv. combines is not enough day to day cleaning. concerning the primary ctr. shaft area, 91 year and newer machines have a plastic tube around primary ctr. shaft , all models 94,95,96. our other problem is operation of header clutch, it has always been designed for idle engagement, not w.o.t. sparks from clutch slipping trying to engage causes chaff around p.ctr. shaft gearcase to ignite. a.e fire in plastic tube. hope fully this will help. bill 9750sts.