For those of you like me who are trying to squeeze every last big of power out of their KLX 250 or D Tracker this simple mod may help. If you haven't drilled holes in the lid of your airbox thinking it was a little drastic try replacing the air duct with one from a Kawasaki Boss, its pretty much the same as the original but shorter and the duct aperture is twice the size of the original.

You will need the help of MR Dremel to enlarge the opening slightly, otherwise its a straight forward replacement.

The part number for the duct is 14073-1734 (274 baht), i also replaced the stock air filter for the K & N KA-1287, i have definitely noticed an improvement and for 274 baht for the duct its worth a try.

You may have to order the part as i did from Chiang Mai as many of the Thai riders have already got in on the act.

Another option is the KDX200 snorkel part# 14073-1577 which doesn't need to be altered, might be more difficult and more expensive though.

I have a Dtracker that is on road only so I just removed the entire lid and snorkel.

I would have removed the back half of the airbox but felt the filter was too close to the exhaust pipe so I left the airbox on, but I cut away most of the airbox that wasn't structural.