In a nutshell, various sources have said that just removing the backfire screen can add 1-2 more horsepower. The problem, however, is that removes the protectionagainst flames shooting out from the carb if your engine should backfire. When it came time to upgrade from the OEM filter, instead of going for the standard UNI or K&N upgrade, I looked around to see if there were other options. This is a 3 part post on how to remove the backfire screen and using a special backfire resistant air filter to provide the backfire protection.

Part 1: The Twin Air Backfire Air Filter for All Yamaha YZ 4 Strokes - Will it work on the KLX250S?

The short answer is "yes".

Here is a picture of the backfire resistant air filter (Twin Air Part No: 152313):



As you can see, its not going to be a perfect fit, since it is not symetrical, like the stock filter, or the UNI KLX300 filter:



Two things to note here are that it's not totally round, and the mounting bushing is not in the center ... both are close enough though:



Belowyou can see that it does fit into the KLX250S airbox quite nicely, though. The air filter is installed upside down, and you can see the "peak" at the top of the filter (now at the bottom) is scrunched up a bit against the bottom of the airbox. This is partially due to the mounting bushing being off-center.


I currently have the KDX high-flow snorkle, and wanted to know if there are any clearance problems ... apparently not:


So, at this point, I'm confident that it fits the KLX250S and I'll take Twin Air's word that the filter is truely backfire resistant and will not cause any issues if there happens to be a backfire through the carb.

On to Part 2 ... removing the KLX250S backfire screen!

 

Nice job! I've heard people saying that it fits, but you are the first person to actually post detailed pic's.

Since it's slightly off-center, does it still fit completely inside the plastic ring mate-up flushfor a nice, greasy seal?