I wash and clean the k&N filter on my wife's heritage then put the oil on it and good to go.it gets cleaned at 2500 mile increments along with the oil change and the rest of the fluids.they might have some info on their site.
CLEANING INSTRUCTIONS
Most K&N Air Filters will normally require
cleaning every 50,000 miles. Servicing your
K&N Air Filter is simple: just follow the
4 easy steps below.
STEP 1: APPLY CLEANER / APLIQUE EL LIMPIADOR / NETTOYER
Liberally spray K&N Air Filter Cleaner or K&N Power KleenTM onto both sides of filter and allow to soak for 10
minutes to loosen the dirt. Do not allow cleaner to dry on air filter.
STEP 2: RINSE FILTER / ENJUAGUE / RINCER
Rinse off air filter with cool low-pressure water from the clean side out in order to flush the dirt out of the filter.
Continue to rinse the filter until all traces of cleaner are gone. It may be necessary to repeat steps 1 and 2.
STEP 3: DRY FILTER / SECAR / SÉCHER
After rinsing, gently shake off excess water and allow filter to dry naturally. Do not oil until the filter is dry.
This was copied from their site