1978 Polaris RXL Service Manual, Page 43Get this manual
PROB LEM DIAGNOSI S
When the fu el-air ixture is ia!1losed as improper du to spark plug read ings, possible co rrection may result if the carburetor is cleaned and its passages blow lea wi co mp ressed airWhen the prob lem exists, fur ther deter min whether the ixtu re is too rich or oo lea n, again using the spark plug firin end condi ion as guideNext use th thro ttle lever to determine at wha egree of throttl valve pe ning the roblem ex istsMix ur Too Rich
Black spa rk plug tip
Heavy exhaust smo e