Some bikes are due a service and the air filters need replacing. I am considering using a K&N filter as they aren’t much more expensive than stock and apparently last longer.
However, I’ve heard bad things such as them making the bike run too lean, being just a gimmick, etc.
Any experiences/knowledge?
Thanks!
Performance upgrade ideally with exhaust pipe jetting/power conander dyno time etc…
free flowing allowing more air into the system, pretty pointless on standard bike, won’t save any money and I suppose it could cause lean running but I doubt it… Just put a new genuine filter in and be done with, if it ain’t broke…
Like he said.
I have a K&N air filter sitting right here but I’m not going to fit it until I make jetting changes.
My bike comes pretty lean from factory as it is, wouldn’t wanna make it any more leaner.
I had a K&N in a ZX9 running a Hindle full system and that used to flame out the exhaust when backing off the throttle. I was told it wasn’t good but I left it because it looked awesome especially at night:P
Poser! 
Here comes the alternative view.
K+N filters are not a performance upgrade and have pretty much the same airflow resistance as the OEM bits if they have been cleaned and re oiled correctly.
Whether they are worth the money depends on the cost difference. For an Aprilia, with their spares prices, they pay for themselves on the second service.
So how long are you planning to keep the bike?
put a K&N on my 'bird seems better on the throttle and fuel consumption, just make sure you seal the airbox down properly, I didn’t and it ran like a pig till I re-did it 
oh and much cheaper the OE Honda 1
