[GoldWingrGreg]

2003 trike

175,000 miles on the ODM

This trike had a K&N air filter installed about 70k miles ago. For anyone familiar with a k&M air filter, its outer frame is made of flexible rubber/plastic material that is not ridged. In other words it can expand and contract. An OEM filter is framed in ridged plastic with an upper and lower lip that inter locks it into the lower air-box as well as the air-box's lid. A K&N air filter only has a lower lip to interlocks into the air box, but it does not have an upper lip to lock into the upper lid. Thus, with a K&N filter, the lid is not interlocked to the filter which is interlocked to the air box. In both cases the two halves are held together with 7 screws.

Below is an OEM air filter.

 

[GoldWingrGreg]

This is what I noticed about the air box with the tank out. The upper lid is not fitting tight to the lower air-box. Between the halves is a ridged OEM air filter with its lips not fitting into channels of the lower air-box.

 

[GoldWingrGreg]

The fat red line shows how far the lower box has wrapped or deformed over time. If anyone is removing a K&N and installing an OEM filter, be sure to check for fitment. I was not able to push on the lower box enough to get the air filter to drop into place.

 

[GoldWingrGreg]

Here are both halves properly assembled with a new lower half that is no longer deformed.

My take away: just because one can go from an OEM to a K&M, does not mean the reverse is true. Certainly a close inspection is required and possibly a new air-box is required first.