Should one avoid cheap air filters from for example aliexpress and similar sites?

[Norway]

Since I live at about 63°28′30″N 11°10′15″E I don't ride the Ninja 250 all year round. When I have taken it out for a new season I noticed that it often struggled to get the rev counter beyond 10 000 RPMs, accelerated slower and appeared weak.
Some tanks of fresh 98 octane gasoline and/or a new air filter have regained some horsepower, from time to time.
Air filters quickly get clogged around here (Trondheim surroundings, Norway) due to lots of rain that mixes with dust due to road works et cetera.
Then my question is: Is it highly recommended to buy the more expensive air filters, or could one so about as well with some from chinese online shops offering air filters for a small fraction of the price of the original parts or other more costly variants? Anyone that knows, or has solid background for own opinions?

[floggolf]

Do you wash and re-oil your filters?

I think the manual sez you can do this 5 times.

If the china foam doesnt get gooey or turn to crumbs, I don't think there would be a problem, as long as the pores in the foam are the same size.

The FAQ at Ninja250.org sez the foam filters perform as well as the oiled cotton and other types.

I just bought a china foam filter, but won't put any run time on it until spring and I live near a rain forest. The air is pretty clean.

[thedrewski86]

I run a foam Kawasaki filter that I got on ebay for $10. I also have a cheap foam no-name filter that was about the same price - I had to trim it to fit but it worked fine too. It's a spare because I would rather run something that came out of a "Kawasaki" box, all other things being equal
I have always been a fan of running factory-spec air filters. If it's still in good shape and needs oil, error on the side of oiling it lightly. Too much happens fast.

[Shafer]

I would suggest getting a Uni Filter NU-2366 for the pregen and oiling it with Belray foam filter oil. (A little goes a long way, don't put it in soaking wet)

The air filter is your only defense from sucking stuff into your carbs and engine. Plus the filter takes a bit of effort to get to, just get a filter you don't need to worry about.

You can get the filter off Amazon for $20. Amazon's filter picture is generic for the Uni Filter NU-2366.

[Norway]

Originally Posted by floggolf

Do you wash and re-oil your filters?

I think the manual sez you can do this 5 times.

If the china foam doesnt get gooey or turn to crumbs, I don't think there would be a problem, as long as the pores in the foam are the same size.

The FAQ at Ninja250.org sez the foam filters perform as well as the oiled cotton and other types.

I just bought a china foam filter, but won't put any run time on it until spring and I live near a rain forest. The air is pretty clean.

I have never washed and re-oiled any airfilter. Wasn't aware of the possibility. Thanks for making me aware. I'll check closer..

[Norway]

Originally Posted by thedrewski86

I run a foam Kawasaki filter that I got on ebay for $10. I also have a cheap foam no-name filter that was about the same price - I had to trim it to fit but it worked fine too. It's a spare because I would rather run something that came out of a "Kawasaki" box, all other things being equal
I have always been a fan of running factory-spec air filters. If it's still in good shape and needs oil, error on the side of oiling it lightly. Too much happens fast.

Thanks for your thoughts on this. I need to do more research on the topic..

[Norway]

Originally Posted by Shafer

I would suggest getting a Uni Filter NU-2366 for the pregen and oiling it with Belray foam filter oil. (A little goes a long way, don't put it in soaking wet)

The air filter is your only defense from sucking stuff into your carbs and engine. Plus the filter takes a bit of effort to get to, just get a filter you don't need to worry about.

You can get the filter off Amazon for $20. Amazon's filter picture is generic for the Uni Filter NU-2366.

Thanks for the advice. Now I'm also aware of "NU-2366"..

[Bob KellyIII]

What you described on the beginning of your post isn't necessarily related to the air filter , but dirty carburetors ! just letting the bike sit with gas in the carbs over the winter can and will gum them up in a bad way....
for over the winter storage I always use a generous amount of sta-bul 360
fuel stabilizer/preservative ....
if you didn't drain the carbs and make sure the gas was not leaking into the carbs past the vacuum operated petcock ( this was where I had problems the leaking petcock refilled the carbs for me!) and use a fuel stablizer too ! you probably have dirty carburators... and the only way to get them clean again is a major tear down of everything on the carburator and clean it by hand...
and use an ultrasonic cleaner and a soda blaster on the internal lines inside the carbs... replace o rings and re assemble and hope to hell you got it all clean again...... I attempted to clean my carbs 3 times the last time I cleaned them was fairly successful I ran it like that for a summer... but it still wasn't perfect
and I knew it... so I pulled them off and sent them to Gordon , Ducattiman
here at this site.... I know carburators ! I am a Retired motorcycle mechanic... but these carbs are the hardest to clean of any bike I have encountered ...so I opted to the expert and let him do it and I am glad I did !
....
these carburators will gum up quickly the passage ways are tiny and the filters that are stock are inadequate to keep the dirt out... thus you get crappy running after the first year...
I think adding a better inline filter would help alot and obviously
properly prepairing for the winter storage...
....
todays fuel does not last that long.... so for my bikes I have been routinely adding Sta-Bul 360 to all the gas on my property....
....
Years ago
I had a 5 gal. can of gas that I had bought in the spring( no stabilizer added of any kind) , and hadn't used it
till late fall or the first of winter.... I put it in the tractor and it fired up but promptly died... over the next 2 days I found the problem... the gasoline wouldn't even light with a match !!!! I drained the gas tank bought new fresh gas and it fired right up and ran like a top....

with gasoline that deteriates so fast now days it is a problem with small carburetors, the smaller the carb, the tinnier the holes inside and when that gas starts clumping up it will plug up those tiny holes.... then the carb doesn't work any more and is dubbed "Dirty !"
and I really think that is the problem here... not a dirty air filter !
.....good luck !
Bob........