1971-1973 Arctic Cat Snowmobiles Factory Service Manual, Page 62Get this manual
ENGINE SERVICING (VVANKEL KM914B) Decarbonizing Decarbonize the sealing elements, their grooves and the rotor after dismantlingRemove only major carbon buildup (flakes) from the sides of the rotorNever attempt to polish or scrape the surfaces of the rotor completely cleanAfter decarbonizing the rotor, refer to Rotor NOTE: instructions on page 54
Decarbonizing the Rotor Casing
Remove the carbon buildup carefully from the spark plug bore and exhaust port with screwdriver or triangular scraper, observing that no metal is scraped offCleanse the rotor casing, wash it when necessary