The vacuum shutoff unit apparently needs only to "engage" the control rod insige the IP, and it works properly even though the shutoff does not pull the external throttle linkage down to the stop position. I started my rebuilt engine this weekend and this is what I experienced. Yes, I had my 17mm wrench firmly gripped in my hand, fortunately it wasn't put to the test. The engine sounds really good but man, it sure puts out a lot of smoke!