Review on K&N Engine Air Filter YA-6602: High Performance Premium Powersport Air Filter for 2002-2013 YAMAHA YFM350R Raptor, YFM660 Grizzly Auto 4x4, YFM660 Grizzly (Black) by Oren Perry

Installed on my 2002 Yamaha Grizzly YFM660. It worked poorly in a lean state for a while and jumped out of the carb again. The OEM filter has been loosened a bit. I took it off and it was deteriorating on the front gasket closest to the carburetor. The foam collapsed. Apparently this got air into the carburetor and the 660 engine doesn't like that so it's running lean. For a new K&N filter, install the front gasket (2 included) to the front of the filter, then apply the included K&N filter grease to it. The setup is VERY tight. It took some effort to get this build into an airbox, but it got through. Everything buttoned up, engine started, idling problems gone. These filters are expensive, but in my case, they were worth it.