Does removing the SMOG actually give any performance gains or are you guys doing it to shave weight off the bike?

Thanks,
Chris

One good question, did all the free mod's and smog on my son's 450 at one time. The wr during break-in and after was two different bikes. Others have suggested doing one at a time but I am a all or nothing guy. Like you I kind of wonder.

I read where the smog removal does not help much for performance, but what is does help with is the popping and backfiring that happens especially when you re jet. What helps performance is disconnecting the grey wire, pull out the snorkel, and there is a part for the throttle that you change out to get more throttle. I did those to my 2007 WR250, and what a difference. I did take off the smog, just to make it cleaner looking. In fact, I now have a whole bag of extra parts off the new bike.

markseaba is correct. Removal of the smog/air pump has no performance
gains. It can cause slight backfiring - particularly with aftermarket pipes,
but proper jetting cures this. Removing it will save a tiny bit of weight and
fee up a bit more space. You can order an AIS removal kit from Yamaha or
the Thumpertalk store. I have an '07 WR250 and left mine in - and the bike
runs just fine. I did replace the throttle-stop screw and cut the grey wire,
but left the air box snorkels in. I like the water protection they provide, and
they are larger than in previous years, so I don't think there's much of a
performance gain by removing them.