Air Filter Misalignment

During a routine stator change, I noticed some new impeller damage on the turbocharger of one of my CX650 turbo's. In the past, every time I would tighten down on the air filter bolt I had a niggling doubt as to whether it was sealing properly. I never pursued it because once the filter is bolted down there is no way to examine the internal seal. Besides, sure Honda pulled a boner on the stator, but surely they could get an air filter to work properly. Right? After observing the new impeller damage, and since the airbox was off the bike, I decided to investigate. I bolted the filter in place, then lowered a dentist's mirror into the intake duct of the airbox. Upon shedding some illumination, I could clearly see that the whole front of the air filter lip was not sealing with the box. An approximately 1/8 inch gap existed. Other members have confirmed this trait on their CX650 Turbo's also. I do not know if it is a characteristic shared with the CX500TC. The filter itself has a one inch standoff attached to it's underside which rests on the airbox. The problem is, through airbox warpage or just poor design, this standoff is not long enough. It does not keep the filter rotated forward enough to allow the filter to seal in the front. Now, you don't suppose a 1/8" rock could cause a tiny bit of damage to an impeller spinning at 150,000 rpm? This is how I addressed the problem. At Radio Shack you can pick up a sheet of self-adhesive rubber footsies which are 1/8" thick. I placed one of these on the bottom of the filter's standoff. I placed two others on the top of the forward part of the filter, where the cover rubber comes in contact with the filter. These effectively rotated the whole filter forward to where it could seal properly. This was confirmed with the mirror. To seal any remaining unseen gaps, I slathered a healthy dollop of silicone high vacuum grease onto the filter seal before assembly. Now when I tighten the filter bolt, I can feel a cinching effect, whereas before it would always bottom before any real resistance was felt. Having personally witnessed the damage to my turbocharger caused by the filter's lack of seal, I would strongly suggest CX650 Turbo owners perform this modification to their filters.

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