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