2007 Yamaha yz 250 2 smoker

Just bought a bills mx2 works pipe and bills mx2 muffler. i couldn't find anything on the internet about proper jetting for the bike with this exhaust system set up. Does anybody have and experience with this and can help me out? I already ordered a jd jet kit and its on its way. Just want to get my bike dialed in perfectly for this season. Thank you for your time

Stock is a great jump off point, i have put 3 different systems on my yz250 and i am still running stock jetting.

pics of it on? Im considering a bills system on my yz,  and did you go full length mx2 or shorty?


please put up a ride report!

Yea you shouldn't need to rejet with just a pipe silencer combo, although stock jetting could likely be leaned out regardless depending on the type of riding you're doing.  Stock is pretty dang good until you start porting, reeds, stuff like that.

Not sure about Bills products as I have not used them, but if you are making changes you'll need to check the jetting as is always a good idea with most any change that can affect airflow into and out of the engine. I have seen some posts indicating going richer and some saying that they were leaner due to the exhaust mods. It's always a good idea to do a plug chop and check the jetting to ensure safe operation. 

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