Deformed air box, it had a K&N air filter

[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.



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.



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.





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.

[Papa Zook]

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.



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.



This 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.





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



Another picture of poor fitment.



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.

Pics are not showing? Were they there when you first made the post?

[GoldWingrGreg]

Pics are not showing? Were they there when you first made the post?

The first post was in the GL1800 trike forum. Yes the pictures were there too. Are you not seeing them on this post ??? I can see them here.

[tfdeputydawg]

No pics for me

[GoldWingrGreg]

Hopefully it is fixed now.

[Papa Zook]

Yep, they work now. What did you do?

[GoldWingrGreg]

Yep, they work now. What did you do?

I had originally copied and pasted my post from the trike forum. When I did, on my end I could see the new post with pictures. To fix, I removed my internet history, and was then not able to see the pictures. So, I removed the pictures from my trash bin to my desktop, and from there edited my post by adding them.

[pwhoever]

I don't doubt your findings but is it possible that the directions were not properly followed when that K&N filter was installed? I was guilty of not doing that on my GL1500. In the directions for the 1800, it expressly states that the o-ring in the base housing needs to be removed. If that is not removed, the filter will sit a little higher in the base and cause a gap between the housing base and the top cover, hence the deformity. Removing the o-ring will allow the filter to sit flush and no gap.

Now I haven't tried the K&N on my 1800 but on my 1500, because I failed to remove the o-ring, I couldnt get a complete closure between the top and bottom. Once I removed it, no more fitment issue. I did save that o-ring in case I ever decided to go back to stock but I never did because that K&N filter served me well...

[GoldWingrGreg]

I don't doubt your findings but is it possible that the directions were not properly followed when that K&N filter was installed? I was guilty of not doing that on my GL1500. In the directions for the 1800, it expressly states that the o-ring in the base housing needs to be removed.

Yes ... at least early on that could have been a possibility. However, this discovery has cause me to re-think what might really be the cause. Often I find air boxes that seem to "snap closed" as the screws are drawn together. Snapped closed meaning that the OEM air filter lip is finally being forced into the upper/lower air box assembly groves as the cover is being screwed down.

In the future I'll be looking at how well the air filter fits into the lower box prior to putting the lid on. I'm wondering if engine heat causes these to naturally fatigue and swell over time. A K&N would allow the swell to be even grater. My Wing, with 160k would be a good one to look at. It has never had anything other then an OEM air filter in it, and never had an belly pan. The reason belly pans can be a factor is because engine heat is slower to dissipate once a Wing with a belly pan is turned off. Although there is no belly pan on this trike currently, usually it has one. Another possibility is that the part number for the air box changed in 2006. I've always assumed for other reasons ... but maybe they discovered an early issue. Unfortunately, I forgot to compare the older style with a newer style prior to installing the new air box.