I am working on my 9660 sts after it has sat inside for the winter. I was going to slow the rotor down all the way so I could adjust drive belt on rotor. I can not adjust the speed down all the way unless I am at Low idle. It will start to come down slightly and very slow but in order to get it down all the way I must be in low throttle position. Also my combine will not allow seperator to run well in low throttle position. It will run for a few seconds but the discharge beater warning light comes on and the seperator kicks itself out. I read in manual if this light stays on this will happen but wondering how i can prevent it. We have 2 identical twin machines and it does not happen on the other combine.