When are air filters considered dirty?

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When are air filters consider dirty and in need of replacement? Sure the OM says to replace at certain intervals, but most don't have hour meters and some my ZT with hour meter says 1 year or 200 hours, which every comes first. Well after almost 6 years, I hardly have 100 hours.
 
If this is a lawn mower then at least yearly. Does it have a foam pre-filter? You can always vacuum it mid season. If you were cutting all nice green grass it might not be a big deal. But if its the middle of the summer with dried grass and dust, then its another story. Leaf time also with a mulching blade will generate lots of dust.
 
Rule of thumb says that when you hold a paper filter up to the sun or bright light and can't see light through it, it's dirty. When it is dirty, I just blow it out with compressed air. I've done in numerous times and it seems to have worked for me.

Oiled filters usually show a build up or film of dirt on the intake (outside) of the foam. Some oiled filters have two layers a coarse outer layer and a fine inner layer. If the exterior layer is in need of cleaning, chances are that both filters should be cleaned.

If a filter is real dirty, it will cause the engine to run rich and in extreme situations, will cause rough running and black exhaust.

Depending on operating conditions, some filters can last a long time. Cutting grass with little to no dust has little effect on air filters. Dry dusty conditions on the other hand can clog a filter quickly and require often cleaning and likely result in much shorter service life overall.
 
Originally Posted By: boraticus
When it is dirty, I just blow it out with compressed air. I've done in numerous times and it seems to have worked for me.


This.

I only replace the element if I see any damage.
 
Originally Posted By: E150GT
when the restriction gauge that the factory didn't install, but you did, shows too much restriction.


You've installed restriction gauges on your OPE air filters?

What are your guidelines on say a riding mower / ZTR vs a push mower vs a weedwacker regarding numerical values for too much restriction?
 
I replace mine every 100k miles. I buy the Injen Nano filter (XX1010)blue and throw a pantyhose layer on top and then my AEM Prefilter. Even when I used AEM Dryflow filter and the cutouts to a buffer pad for prefilter in my intake resonator all my filters stay clean.UOA's show virtually no particles. Been running the Injen Nano / AEM Dryflow types since 2013.
 
It's harder to tell with a constant-speed engine. With a mower, if you aren't able to mow as much a path as you are used to it's either the blade needs sharpening, the AF needs cleaning/replacement, or the valves need adjusting, if adjustable. In my experience.
 
Originally Posted By: NH73
When are air filters consider dirty and in need of replacement? Sure the OM says to replace at certain intervals, but most don't have hour meters and some my ZT with hour meter says 1 year or 200 hours, which every comes first. Well after almost 6 years, I hardly have 100 hours.


From an engineering standpoint, they are considered "dirty" when they are restrictive. You can ad a cheap restriction gauge (available at most truck parts stores) to any air cleaner housing on the dirty side
 
^^^^ I can't believe this dicussion on installing restriction gauges on OPE air filters has made it to this level of a Technical Training Director of a major filter manufacturer.

Motorking, I'll ask you the same question I asked earlier in this thread.

What are your guidelines on say a riding mower / ZTR vs a push mower vs a weedwacker regarding numerical values for too much restriction?
 
My mower with a B&S 550e engine has a foam air filter. The mower gets hard to start when the filter is dirty from the air restriction and is acting as a choke. That’s when I know the filter is dirty and to clean it. Happens once or twice a year.
 
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I decided blow out the air filters this time. They still look a little dirty, but I can see light through them. Also got myself a spark plug gap gauge. They checked good. Don't need to buy air filters and spark plugs. Might as well get as much life out of them as you can.
 
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