1968 Evinrude Starflite 100 HP outboards Service Manual, Page 50Get this manual
Carbon accumulation in the exhaust ports restricts the flow of exhaust gases and has considerable effect on performance of the motorCarefully scrape carbon from cylinder he,ds and exhaust ports with scraper or other blunt instrumentExhaust ports and all exhaust passages must be free from carbon deposits to insure maximum performanceAvoid getting carbon in water jacketsDO NOT scratch cylinder head surface of cylinderWith continued operation of the motor, the cylinder walls will take on glaze which reduces the effectiveness of the seal between the piston rings and cylinder wallsThe result will be reduced compression and decrease in performance of the motorBefore reinstalling the pistons, break the glaze by using fine cylinder hone to refinish cylinder wallsA few up and down motions of the tool should be sufficient to remove cylinder wall glazeSee Figure 5-21Figure 5-22Surfacing Cylinder Head To check for flatness, lay sheet of No120 emery cloth on surface plate or piece of plate glassPlace the part to be surfaced on the emery cloth and move slowly back and forth several times in figure motion, exerting evenly distributed, light pressureIf the surface is actually warped or sprung, high