A standard KTM air filter does its job. But only if the element holding it is sealed!! KTM 690 airbox, however, has a tendency to let some air in on the sides… The only question is – where?
To help seal, some users put grease between the filter and the lid, others change airbox for the accessory filters mounted directly on the throttle body intake, eliminating the mentioned box at the same time. In my opinion, the concept, the shape of the airbox is well considered by KTM in our motorcycles and I do not want to change it. The filter is placed under the rider’s seat, above the engine. Highly set air intake point creates a route for air which first has to go up then to be sucked down. It acts as a syphon – blockage for water being sucked in and reduces the risk of engine flooding.
I watched a video on the Youtube, where one of the KTM users struggling with dust, connects the vacuum cleaner to the airbox, seals all air inlets and then throws dust at the box. It was clearly visible as it sucks particles. It was similar to cigarette smoke. Applying a large amount of grease at the filter’s contact area should eliminate the problem.
I noticed small dust particles at the first inspection of my motorcycle. After investigating the structure more closely, I found points where the box opened up, giving the chance for dust to bypass the filter. This is exactly on the connection between the flange, where the filter is installed, and the bottom part. As new airbox costs a lot and the repair is quite simple, I went for a DIY solution. A two-component epoxy glue has done the job. Applied on the outside, it filled up gaps without any risk of crumbled (due to vibration and time) material falling inside and being sucked into the engine. I did not find a similar problem in Monia motorcycle, but to have peace of mind I did the same thing in the place where it occurred to me. A few rides later and it seems stratifying problem has disappeared. However, air suction around the filter was still unknown to me.
I was pretty surprised when during a visit at KTM centre to buy a rocker arms I was informed about the service carried out – replacement of the KTM 690 airboxes. The reason among other things – faulty connections which I have already fixed myself. Motorcycles are already after a visit at the KTM workshop and so far, the problem of dust has not returned. It is also possible that this is due to the decision to replace the original air filter with an accessory Twin Air filter. Its plastic casing is very tightly fitted to the flange and has a gasket in the bottom part – a place many people have identified as the point through which dust gets in when using a standard filter. To make sure it will adhere well to the surface, I attached a thin window seal to the cover. It makes filter firmly pressed to a base. I made the seal test more or less the same way as the aforementioned 690 user. The vacuum cleaner attached to the point where the throttle body normally is attached, holes sealed and the flour dropped on it. Airbox did not suck dust in. Success! If the situation does not change over time, I consider the solution to be effective.
The new filter is made of a layered sponge, soaked in oil. It gives a better airflow while maintaining a good level of filtration. And of course, it is reusable, which at the time that we plan on the road, takes from the head the problem of looking for standard filters.