My 860 had an overheating problem last year, tried most everything . It turned out my rad was shot. Have you pulled the rotary drum so you can inspect the rad more closelyIJ My rad was plugged, no air was getting thru. Took it out to a rad shop for a better inpection. The fins between the tubes were shot. They combed them back into place but folded back over too easily blocking air flow.I had the rad rebuilt. Since the new rad has been installed no overheat troubles.