Originally Posted by gaw777
So who has done the airbox mod like BDSB? I have drilled the holes in the side cover to allow more air, but they also removed a portion of the top. Necessary?
Maybe just remove the snorkel?
A little reluctant to cut the top of the box off.
Feedback from anyone who has done this would be greatly appreciated.
Lots of holes in the air box was a very popular modification of the Yamaha WR250R and it helped a lot.Removing the snorkel from other motorcycles I have had (XR400R & KLR650) seemed inconclusive. From a fluid mechanics standpoint, removing the snorkel seems to trade a smooth tube with a reduced cross section with a sharp edged hole with a larger cross section for a net gain of possibly nothing. For sure removing the snorkel you'll make more noise. Having said that I bought a spare CRF airbox lid, and airbox. They are 8 and 18 dollars respectively so I can hack them up...If I don't like it, I can go back. Perforating the lid does work on XR400's, but of course it makes fording deep streams dangerous. Also, removing the backfire screen and the aluminum sheet with the larger perforations from the stock filter may be troublesome also. The large perforation sheet probably acts as a stop to keep the folded paper filter from turning itself inside out. For those who have done this modification, I'd suggest they check the filter very frequently looking for rips...just hold it up to a bright light. Since a single cylinder engine has lots of pulsing in the flow, that folded fabric is constantly beaten back and forth. I'm hoping Twin Air or other knowledgeable aftermarket filter folks come up with a foam filter for the CRF. Twin Air already makes one for the CRF250R.