K&N Air Filters

K&N advertizes more performance.

However, I note the Dynojet fuel maps are the same for "stock or aftermarket
air filter".  They have a gazillion maps, one fore each kind of
pipe/muffler.  They care about pipe type but not a bit for air filter type.

If it doesn't make enough difference to change the fuel map it isn't making
any real difference.

I think the anecdotal evidence of greater performance with a K&N is just the
change of putting in a new filter.  I've also had a performance increase
with a new paper filter.


I did an experiment.  I put a thin layer of grease downstream of the stock paper air filter on the FZR1000 I used to own.  Then I rode around for a while.  I pulled the filter and inspected the grease.  It was a clean as the day I put it there.

Then I installed a brand new well oiled K&N air filter.  Rode around for a while.  Pulled the filter and inspected the grease.  It was dirty.  All that dirt made it past the K&N.  The dirt was stopped by the stock paper filter.

I threw the K&N away.

Pistons don't like grit rubbing between them and the cylinder.  The grit acts like grinding paste.  It co$ts more to replace a set of pistons these days than to buy a whole low mileage replacement motorcycle.  I want my pistons to last as long as possible.  It's stock paper filters for me from now on.