A pair of centrifugal governor are combined in {HEAD ~ an unit} for providing {TAIL ~ a compound spark advance characteristics} 
A pair of centrifugal governor are combined in { HEAD ~ an unit } for providing { TAIL ~ a compound spark advance characteristics }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL