Cutting hay yesterday my 6215M started to idle down and then speed back up all by itself. Running a NH 1411 conditioner at 530rpm then it would drop down in somewhere around 480 if I throttled back up to 530 it might stay there a while and surge up to around 570 or more. Called dealer and spoke to service manager who I trust and he said sounds like trash around the pickup tube in fuel tank. This sounds plausible so how hard is it to drop fuel tank and clean out?