I clean the filters regularly with compressed air. I’ve never noticed any damage to the filters. They were properly sealed. Each time I’ve cleaned them, the plastic air intake where the butterfly is, is always clean.
The only one I’ve had problems with sawdust getting past the filter was on the 500i which I ordered the Eagan air filter kit the first week I had that saw.
I personally don’t think it is front ingress of fines because I always maintain my equipment and take care of it and I would have noticed if it was dirty on the plastic where the air filter seals.
Now if it was carbon build up from the stihl ultra oil and damage from the carbon, I wouldn’t be surprised.
The only one I’ve had problems with sawdust getting past the filter was on the 500i which I ordered the Eagan air filter kit the first week I had that saw.
I personally don’t think it is front ingress of fines because I always maintain my equipment and take care of it and I would have noticed if it was dirty on the plastic where the air filter seals.
Now if it was carbon build up from the stihl ultra oil and damage from the carbon, I wouldn’t be surprised.