See Figures 1 and 2
The crankcase oil filler breather cap should be removed and cleaned every six months or 6,000 miles. After removing the cap, wash it in a low-volatility, petroleum-based solvent (e.g., kerosene). Probe the breather holes to assure removal of any accumulated deposits. Shake the cap dry and install it. With the advent of the closed crankcase ventilation system in 1968, the filler cap must be disconnected from the connecting hose to the air cleaner before cleaning.
Do not dry with compressed air as filter element damage may result.