In Part 1, we confirmed thata Twin Air YZ backfire filter can fit the KLX250S.

In Part 2, we saw how to remove the KLX250S backfire screen.

Here in Part 3, we'll tailor the Twin Air filter for a custom fit.

Here is a picture of the modified backfire screen from Part 2, along with the Twin Air backfire filter. The filter is shown with the KLX250S air filter basket inside:


The YZ filter is not completely round - it has a little "corner" sticking out, as shown below:


Just poke it in ... it goes in easy and still seals nicely. In Part 1, I mentioned the filter's mounting bushing is not centered in the filter. The picture below shows how the filter is distorted a bit to get the air filter bushing to fit on the inner frame bushing. Also, since the filter has a "peak" on the top, it getsscrunched down a little when the air filter wing nut is tightened. All in all, its a pretty good fit, though:


Well, not exactly:


The OEM filter has a 4 3/4" opening, and the YZ filter only has a 4" opening.With the filter wing nut tight, the white airfilter frame clamps the foam against the backfire screen frame, making it easy to trim with an X-acto knife. Here's what it looks like after trimming:


The modified backfire screen frame goes back into the airbox, then oil the airfilter& put grease to seal the edges, and ... Presto! 1-2 more horses!!! (At least that's the theory.)

Note that this is a significant change to your airflow, so there's probably a corresponding jetting change needed. (But you already knew that going into this whole ordeal, right?)

That's the mod, but there's no ride report to go with it. (It was -20 C outside today, so the ride report will have to wait for warmer weather.) If you get a chance to do this mod and get out riding before I do, pleasepost your results!

For anyone who's interested, there are more photos available here: http://s143.photobucket.com/albums/r...fire%20Screen/

That's it for now!

Mike

 

[sm=bounceybounce.gif][sm=bounceybounce.gif][sm=bounceybounce.gif][sm=icon_cheers.gif] Nice work!

 

Waiting on a report on someone who has done this to see if it is really worth it. how big ofa change is it?

 

Nice job, Mike!

 

A great informative post!!! Hats off to you.

The air filter is being ordered for another part to fill up my suitcase of parts back to Thailand. Thank you.

 

Wow Mike,

Killer job man. If that eaks out 1 to 2 pony's I'm in!! Thanks for leading the way with a great how-to photo album!!!!

 

I too am anxious to know if doing this really and truly adds to the power. I'm honestly sceptical about it. If the backfire screen were built like the one on my XL600 then it would be easier for me to swallow. The screen on it is made from a material that looks like loosely woven steel wool. But the screen on our KLX apears to to have almost no restriction at all. I'm thinking that if I were to want more air then the airbox lid is an option or a high flow filter.
Oh well, just thinking out loud here. Keep us posted as to any power inprovements!