If I install the K&N air filter for my '99 F4 am I going to need to install a jet kit as well, or will it not mess up the fuel air mixture too much?

 

I've been told yes and no, I think if you stick with the "street" K&N filter and dont go with a race filter it should be okay... but you'll never know until you try.

Also, get the single big filter to replace the OEM one, dont get the 4 individual cone filters, then you will need rejetting I'm fairly sure.

Let me know if it messes yours up, then i know whether or not to get one :P

 

If you put on a new filter system, I would recommend doing a jet kit upgrade. New systeme meaning anything radically makes your
bike take in more air, meaning making it run more lean.

 

get the filter install it see how it runs some need rejeting some don't my f2 didn't my 929 didn't but some guys say theirs did....

 

but then again my 929 is fuel injected so no jets hehe

 

Depending on where you ride. Altitude can play a big part. I have a full race exhaust with stock air fiter and did not need a jet kit. My bike was setup for sea level where it was running rich and now 6000ft above sea level, it runs perfect!

 

I wouldn't get a K&N.Carbed bikes make more power with paper and the stock airbox.

 

Why would more airflow from the K&N filter cause less performance? I'm not totally a dunce, but I don't really understand the logic in that.

 

Ok, so I installed the K&N filter, and there are no flat spots or hesitation. It's real smooth through the power band. I don't feel like there was a huge performance increase, but I suspect I might be running lean, because I have been having some temperature problems. in a week or two I am going to test the bike to see if it's running lean. If it is then I will rejet (I might do this eventually anyway.

I am at 500 feet also, so that may be why its not so lean that I'm having noticeable problems.

 

I threwa K&N in my 2000 f4 a few months ago and love the way it runs now... my stock filter was pretty ugly though.Iimmediately noticed animprovement from 5k to 9k rpms.

I'm at sea level with no jetting.