Air Filter Question/Idle trubles

[Its_a_Honda]

I have a 1999 400ex Stock for the most part, i cleaned my air filter out the other day and I went to gently wash my air filter and obviously it was old and i need a new one cause it ripped on me. Any suggestions on a nice but not to expensive air filter. Then when im sitting there in neutral just letting it idle it will stop and make a clunk sound. any suggestions?

[powerbomb400]

I myself use Twin Air. Alot I'd folks like the Uni filters. What I use are more expensive but I run them for years and have always gave me good service. Most likely need to clean the carb since the other filter was getting worn. It could have let dirt in. The clunking sound when it dies is had to determine without hearing it for myself. My starter makes a sound sometimes.

[kt1148]

I bought a No-Toil air filter because of the very simple way you clean it. I also still use the OEM filter when the other one is drying.

[2001400exrida]

is the clunk sound like a back fire through the airbox or what kind of clunk are we talking about? Sometimes if they're lean, they will kind of miss at idle and it sounds like it's pushing air back through the box.

Far as your air filter, the uni's are probably the most affordable and the best at filtering, i believe you can get a new uni for $30 or less and it should last you quite sometime, just make sure to get some filter oil with and keep it clean and oiled regularly.

[81dasher81]

i agree on the uni... but whatever way you do decide to go, do not got k&n! lol

[Its_a_Honda]

i rebuilt the carb a few years ago its probly time for another. i went with a K&N with the bag. and it sounds like its the piston, ill post a video after i get my air filter on.

[Its_a_Honda]

iv heard good and bad about K&N so i decided to try one out and see for myself lol. i guess its mostly a maintenance thing i guess. if i dont like it or feel its suckin dirt ill try out something new thanks for the help guys

[DragonGunner]

iv heard good and bad about K&N so i decided to try one out and see for myself lol. i guess its mostly a maintenance thing i guess. if i dont like it or feel its suckin dirt ill try out something new thanks for the help guys


Running K&N for 13 yrs.....same ones. Run with your outerwear over it...when it starts to run kinda rough, take the outerwear off and it will run perfect again but its time to clean. Get a bucket of hot water and DAWN dish soap and a scrub brush and hit if for a couple minutes submergeing the entire filter under water and then rinse with hot water. Shake filter and then let stand to dry...I like a nice windy day, let dry for the day....if in a rush you can use a hairdryer to speed things up. Then spray a coat of K&N oil on it, going up and down the pleats. I like to let it stand for a few hours like that, wipe off excess. Wash the outerwear the same way and when dry cover the filter and your good to go.

[81dasher81]

i dont have a problem with k&n maintenance, its really not a big deal. i dont like them because as soon as you pull the head off a motor you can tell if it was a k&n or not.. ive had 3 400ex's and 2 450r's apart that all had k&n's with outerwears and you can see a build-up of dirt on the top of the piston which shouldve been caught by the filter (and no, its not just carbon). that's why i run a uni. i think its well worth it for a uni.

[Its_a_Honda]

Running K&N for 13 yrs.....same ones. Run with your outerwear over it...when it starts to run kinda rough, take the outerwear off and it will run perfect again but its time to clean. Get a bucket of hot water and DAWN dish soap and a scrub brush and hit if for a couple minutes submergeing the entire filter under water and then rinse with hot water. Shake filter and then let stand to dry...I like a nice windy day, let dry for the day....if in a rush you can use a hairdryer to speed things up. Then spray a coat of K&N oil on it, going up and down the pleats. I like to let it stand for a few hours like that, wipe off excess. Wash the outerwear the same way and when dry cover the filter and your good to go.

Okay thanks, like i said iv heard good and bad from what i can tell its mostly about how clean you keep them. I feel a difference for sure i got way better throttle response and a little unexpected power.

[Its_a_Honda]

i dont have a problem with k&n maintenance, its really not a big deal. i dont like them because as soon as you pull the head off a motor you can tell if it was a k&n or not.. ive had 3 400ex's and 2 450r's apart that all had k&n's with outerwears and you can see a build-up of dirt on the top of the piston which shouldve been caught by the filter (and no, its not just carbon). that's why i run a uni. i think its well worth it for a uni.

Im going to ride with the K&N for a few months and do a rebuild (which is greatly needed) and see how it looks if i dont like the look on the inside im gonna try a uni or an OEM
thanks for the help everyone

[DragonGunner]

Im going to ride with the K&N for a few months and do a rebuild (which is greatly needed) and see how it looks if i dont like the look on the inside im gonna try a uni or an OEM
thanks for the help everyone


Thats going to be hard to judge....if you don't know what the piston looked like before.....? I have done several rebuilds and never found "dirt" on top of any of my pistons......

[81dasher81]

Thats going to be hard to judge....if you don't know what the piston looked like before.....? I have done several rebuilds and never found "dirt" on top of any of my pistons......

thats a good point dragon, you won't have anything to compare it to..

i guess some people love them, but i havent had a good experience like i said. i havent priced a k&n in a while but if i remember right, the uni's less expensive. i clean mine every two rides or so, so like i said i dont have an issue with the maintenance

[Stickman400]

I had a K&N and Outerwear on my 400 since the day I bought it brand new nearly and when I tore it apart for a rebuild 2 years back it was nothing but carbon build up inside. I even took pictures after I popped the head off and posted them up here when I did it. I think if you don't care for it or run without the outerwear for any amount of time that's what does it. I've switched to a UNI myself just because the K&N takes a lot longer to clean that the UNI. I know I could buy 2 K&Ns and swap them out during cleaning, but $120 for 2 K&Ns vs. $60 for 2 UNIs which are easier and faster to clean?? It's a no brainer.

[DragonGunner]

Carbon buildup IMHO is from gasoline, to low of octane, running way rich, plus after 1995 they slacked off on how much detergents were put in gas. It also come from a plug not firing up to standards. So if a filter is running dirty, then your running rich....this can happen to any filter also. I ran over 2 yrs on a 426 using only 100 octane and a Splitfire 416 plug. When I tore it down it was a light tan color on top of piston, no carbon build up. When it was stock and I tore it down there was carbon build up but was running 87 octane. So I think its the gas and jetting more than anything for carbon build up.