I ordered the NOS adapter and Uni filter for my Z400 mainly becasue I did not care for the factory air filter seal. Now my question is will running this cause the bike to be lean and do I need to rejet. I was not too sure how much more air it let in or if it mainly just made a much better seal.
Thanks

 

Yes, you do have to rejet. I believe i went up to a 140 main jet. you don't need to do much more than change the main jet. i can't remember if that was the correct size though. Hopefully someone with a better memory can he you out.

 

If your pipe and air box are stock, you will not have to re-jet. If you plan to run with the lid off you will have to bump up the main jet.

 

Right now everything is stock, I mainly got it so I was sure no dirt was bypassing the suzuki filter. I felt that it was not a very good design. It seems like the bike is just a shade rich right now (from the factory) so I was hopeing it would balance out and not need rejetted. It is funny, I will put a top end in the bike without worry about it, tear the entire thing down to the frame, but I just dont know crap about carbs or jetting. That little silver rounded box with needles and jets scares the heck out of me. I feel like if I mess with it the motor will never run again. I think I need to take a carb rebuilding class or something. Thanks for the feedback and more is always welcome

 

You should be fine with the OEM jetting. If you do get a pipe later, do a search for "Z400 jetting" you get tons of related post.