07-05-2016, 03:10 AM
"Should we just replace it even though it "looks" clean? "
I work in the chemicals industry, we deal with a lot of powder transfer with associated bag-houses and filters. Filter technology has improved quite a bit since the 1970's, but there are still limits. What we see in the industrial setting with trying to re-use filters that have been "blown out" to clean them is they are much less efficient compared to new. Your eyeball measurement just isn't good enough to detect filter damage/pluggage on a used filter. There are two types of pluggage - what you see on caked up on the surface of the filter, and what you can't see embedded down in the pores of the element itself.
Rapid fouling from dirty conditions leads to the caked up mess, and this type of pluggage can occur quickly. The caked up mess is what you remove whenever you blow them out / vacuum them off / or just shake them real hard. This is sometimes good enough to stretch a filter's life, but does not bring it back to like-new condition. Plus the act of blowing high velocity (compared to normal design velocity) air across the filter can damage it. However, if the caked up pluggage occurred over a single know incident (say - a long trip down a dirt road), then blowing off will allow you to continue using the filter up to it's normal life span.
The embedded pluggage generally will not clean off by blowing / vacuuming / shaking. It's there regardless, and you can't see it. These are smaller dirt particles that are actually in the filter mesh, down in the actually pores, plugging them. This type of pluggage usually occurs over a longer time frame and is the key to the filter life expectancy. Once it's reached, buy a new filter. Blowing them out won't remove the embedded particles without damaging the filter.
Now the above is industry experience, not motorcycle experience. I'm as cheap as they come and normally very tempted to blow out and re-use, but all my experience in industry tells me that it's cheaper to just replace on the recommended frequency. Think of it like insurance.
FYI - The K&N style filters are a different technology, using the oil to help maintain filter pore integrity and allow proper cleaning. I don't have nearly as much experience using these, but will most likely switch to this style whenever the original stock filter needs replacement. All the above is based on dry filter experience.
I work in the chemicals industry, we deal with a lot of powder transfer with associated bag-houses and filters. Filter technology has improved quite a bit since the 1970's, but there are still limits. What we see in the industrial setting with trying to re-use filters that have been "blown out" to clean them is they are much less efficient compared to new. Your eyeball measurement just isn't good enough to detect filter damage/pluggage on a used filter. There are two types of pluggage - what you see on caked up on the surface of the filter, and what you can't see embedded down in the pores of the element itself.
Rapid fouling from dirty conditions leads to the caked up mess, and this type of pluggage can occur quickly. The caked up mess is what you remove whenever you blow them out / vacuum them off / or just shake them real hard. This is sometimes good enough to stretch a filter's life, but does not bring it back to like-new condition. Plus the act of blowing high velocity (compared to normal design velocity) air across the filter can damage it. However, if the caked up pluggage occurred over a single know incident (say - a long trip down a dirt road), then blowing off will allow you to continue using the filter up to it's normal life span.
The embedded pluggage generally will not clean off by blowing / vacuuming / shaking. It's there regardless, and you can't see it. These are smaller dirt particles that are actually in the filter mesh, down in the actually pores, plugging them. This type of pluggage usually occurs over a longer time frame and is the key to the filter life expectancy. Once it's reached, buy a new filter. Blowing them out won't remove the embedded particles without damaging the filter.
Now the above is industry experience, not motorcycle experience. I'm as cheap as they come and normally very tempted to blow out and re-use, but all my experience in industry tells me that it's cheaper to just replace on the recommended frequency. Think of it like insurance.
FYI - The K&N style filters are a different technology, using the oil to help maintain filter pore integrity and allow proper cleaning. I don't have nearly as much experience using these, but will most likely switch to this style whenever the original stock filter needs replacement. All the above is based on dry filter experience.