ST1100 replacement K&N air filter trouble


After placing the K&N filter, the bike held back in the lower rpm ranges. A little bit of experimenting led to a solution.

When I obtained the bike, a visual check of the placed original Honda air filter (12711-MT3-000, Element air/cleaner), showed a filter looking like new.
However, fuel consumption started to increase and despite the good looks of this filter, I started having doubts about it's functioning.
An extensive internet search learned that besides the expensive original filter, there are several alternatives. Reviews show that one should have doubts regarding at least some of the aftermarket products. One did however stand out and that was the K&N filter. Though slightly more expensive than the original Honda filter, this filter should last the lifetime of the bike, whereas the Original filter should be replaced on yearly basis.

 

Below picture shows the K&N filter as I acquired it. Note on the right side of the circular filter, in the bottom of the filter housing the air intake openings for the filter.
The bike did however, not run optimal with this filter. It held back in low rpm. This is due to the filter being more "open".(Letting air through with less restriction than the original Honda filter.)

 

I learned that the filter has been delivered in the past with a foam collar that should restrict the flow through the filter somewhat, thus leading to flow similar to the original filter.
Since mine was delivered without the foam collar, I asked around on the Dutch ST forum and got one from another Pan rider who did not use it.
The below picture shows the foam collar in place. Note how it blocks about 50% of the air filter housing intake openings, whilst also strongly reducing the size of the flow channel around the filter.
As a result, the bike starts ands runs fine in low rpm, but opening the throttle above 3500 rpm, leaves the engine with insufficient air. I could hardly reach speeds over 120 km/h.

 

So, the search was on for a filter collar delivering a similar restriction in air flow as the K&N foam collar, but with less than half it's thickness.
In our kitchen we use a very common 3 mm filter cloth in the hood, (Air suction device) I cut this to the correct size and my wife sewed the ends together.
This material does not stretch as well as the foam collar, so make it a little larger to prevent fitting problems.

 

Here we see the new collar in place over the K&N filter. Note that the air intake openings are now completely free, whilst also there is a large space around the filter for air flow.

 

The bike now runs fine, without holding back at low rpm, whilst there is also sufficient air for max throttle at high rpm.
Time will tell how this collar holds, but should it need replacement every now and then: The material is cheap, comes as one large cloth, good for cutting many out of it, and above all, one can get it at many places.