I have 2 K&Ns and keep one clean at all times, when I change oil, I put a fresh K&N in and then clean the other one...
yo bee
this way you can be 99.999999999% sure that your air filter never can cause any problems.
but at least with the k&n your way of acting is comparable to using a suspender in addition to a belt.
because:
you can leave a k&n in there for 40,000 km with complete peace of mind until you blow him out with compressed air and then leave him alone for the next 40,000 km.
then at 80,000 km you should clean it with the cleaner from k & n and rewet it with their special filter oil, let it "dry off" and then reinstall it.
that's how i do it and I've never had any problems, no matter where a k&n has been used so far.
so much for reassurance for you and everyone else.
and to all those who fear with a
standard! k&n the engine could become lean and thus get a combustion that is much too hot,
i can personally give the absolute all-clear,
because the amount of air that the filter (when clean) can let through (its flow-rate) is always bigger than the amount of air that can go through the ports and throttle valves (carburetors) at all.
(what about the
racing - k&n, i have no clue)
the following:
years ago i saw a test setup where you could cover half of the k & n with your hand and still go through 70% of the intake air.
small exception regarding heavy soiling / clogging:
if you have for instance to go through a sandstorm (or similar) with the k&n, you should then blow out the filter with compressed air as a precaution.
regards
the ol´ man from across the pond