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Which Air Filter

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On my 450X I like the TwinAir powerflow system, with the special flame retardant filter and billet cage, with no screen on it. That, with a Napalm Racing attachment screw to secure the filter makes removing and replacing the filter way,way easier. The precision of the fit is miles better than stock, and I mean the one without the inner ring. With the inner ring it's probably even better.

Also with this combination per JD, with his kit, I can run a 170 main, up from a 165 ,with super throttle response, tan plug, no stalling , no bogging, no back firing.What's not to like about that ?

I see a lot of curt, 2-5 word replies on this site to folks who are asking an intelligent/important to them question. Unfortunately the replies they get aren't always intelligent whatsoever. Kind of, high school, isn't it ?

And, what does "Stock Filter is best" all about ? There's nothing special or " best" about it. I thinl it's the sorriest piece of equiptment on an otherwise beautifully engineered and built bike. Doug

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The stock filter is best.

Okay let me qualify my statement. I've been racing at A level for about 25 years. I've used just about every air filter ever made in my bikes. The stock Honda filter is, hands down, the best filter for the CRF450. All the aftermarket filters are 5/8" thick. The Honda filter is 3/4". Look at how much effort Honda puts into the sealing ring. The rubber ring is glued AND sewn to the element. A foam ring is also glued to the rubber sealing ring to make for a perfect seal to the airbox. You can wash them many times over and they stay together. It's Honda quality, through and through. Sure it's tough to get in and out of the airbox but once you get the hang of it, it's easy. Twin air actually makes their filter SMALLER so that it's easier to get in and out of the airbox. A smaller, thinner air filter is not what I want in my 450.

RHC is a professional engine builder that builds some of the fastest CRF's in the country. You ought to listen to him when he says the Honda filter is best.

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I completely respect RHC's opinion. I also completely think the stock filter is not as good , and that in this case size/ thickness doesn't matter.

I've ridden with them in sand, mud, monsoons, never seen a speck in the intake track. I use Belray filter oil, clean 'em with kerosene then soap and water, no problems ever .

I've used TwinAirs for years and will continue. They were OEM on my Katooms, never a problem. The stock filter cage I think is junk, has sharp edges, and a sloppy fit. I they're good for you, keep running them. Not for me, though. Doug

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i was wondering this also. I have a twin air and i trashed the stock one after a trip to sand mountain. I notice that twin air doesnt glue the rubber grommet to the filter. is this a problem. I pulled it away from the rubber when it was dirty and there was no signs of dirt passig by.

A friend of mine said that twin air filters were causing all the intake valve problems on the hondas? Is there any truth to this ?

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The stock filter cage I think is junk, has sharp edges, and a sloppy fit. I they're good for you, keep running them. Not for me, though. Doug

The stock cage is designed to work specifically with the stock filter. If you attempt to run an aftermarket filter with it, you will get a sloppy fit. This can be illustrated by installing the cage in the airbox without the filter in place. You will find that the cage comes about 1/8" shy of mating to the sealing surface of the airbox. This isn't a problem with the stock filter because of the rubber and thick foam of the stock filter more than make up for that 1/8". When an aftermarket filter is used with the stock cage, you can literally pull the filter off the cage even though the wingnut is completely tightened. Try it, you won't like what you find.

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for dirt only use,ive found the stock filter (no screen) to work the best.

the KN Xtreme is a different story if you run some pavement.

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I like the stock filter except the foam sealing ring is easy to pull off if you aren't carfull removing it from the air box. I also use the twin air with there cage . I agree that a twin air with the stock cage is a risky fit. I think it comes down to time and attention to detail with each one when installing them and clean them after every ride. I have

2 05 450r's one the valves went out on (stock filter) and the other is still good. (use both filters). hope it helps

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Thats quite true about a TwinAir with a stock cage.Thats why I dont use the stock cage,either. Or, the crappy fixing screw. The Napalm Racing replacement screw is a very high quality little item that for 14.95 is a steal and definetley makes life easier, and filter swaps faster.

The TwinAir billet screen works beautifully though. Doug

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What abought running a stock filter and removing the backfire screen? I just tried this on me 05 450 and the throttle response is good, but it will not start cold as it did before.It will not start with the choke on when cold but if you pull the hot start in [making it leaner] it start every time cold! It also has a White Bros carbon pro exhaust.Any thoughts??

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What abought running a stock filter and removing the backfire screen? I just tried this on me 05 450 and the throttle response is good, but it will not start cold as it did before.It will not start with the choke on when cold but if you pull the hot start in [making it leaner] it start every time cold! It also has a White Bros carbon pro exhaust.Any thoughts?? And sorry for being a newbe. I will now STFU!!

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Saw - we have all been a newbie at one time- don't sweat it. Glad you've joined us thumper-geeks!

I've been running w/out my backfire screen on my 05X w no probs although some swear you will end up toasted - but I doubt it!

I believe you should rejet your bike. Even slight changes like a backfire screen can effect your jetting, but big changes like a pipe will really make a difference. PM Burned. He is DA MAN :banghead: on jetting changes.

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i did have the stock filter in without the backfire screen and last week i got the twin air and it is a thinner filter than stock and i still left the back fire screen out,u can tell a difference from the stocker filter

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And? Nobody's perfect...

And a shot of 3M77 and thats all fixed up.

Nope, there's nobody perfect, but Ken is a known expert on CRF's and I tend to trust him completely. He bends over backwards to help people with there problems and questions with their bikes. I'm not busting you out Shaun, you've posted some really good info. yourself ,and I've enjoyed reading what you've had to say quite a few times.

3M77 is magic stuff. I've used it to put graphics back on my chest protestor, on my r/c model aircraft hobby, and tons of stuff around the house. Once that stuff sets up, man does it hold ! Dries clear,too. Doug

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