ok, my Z400 has an hmf pipe, uni air filter, and i went from a 130 jet to a 137.5, i get goin and at half throttle it starts to bog down and spit and sputter and just the kinda noises you just dont wanna hear, what may be my problem?

 

Still way too lean. Lid on 145-150 Main & lid off 165-175 main. All depending on altitude & air temp of course.

 

thanx for the info but why would it cut out with that little bit of difference.

 

becuase for the mixture for air/fuel needs to be right and if you are lean you need to get more of each which cat is right that you would need to upgrade the jet I would prob go with a 137 for just a slip on.

 

thanx for the info. on the problem, i stuck the lid back on and road around and it was fine after that, i got my info.s mixed up and i thought someone had said on another forum to take the lid off and it would help, they didnt specify about the jet size. had a brain fart and didnt think to leave the lid on, thanx for the info

 

well thats good to hear cya later.

 

its better to take the box completly off and keep jetting up till there is no bog or poping of the exhuast, if u get goin half throttle and let off and u hear poppin that means your to lean keep jettin till it doesnt or run a lil lean im lean by a size or 2 but LEANER THE MEANER

 

Pull that lid off!!! If you're running stock Mikuni jets (i.e. not Dyno-Jet,FMF, Moose etc.) bump up to a 165 or 170 Main jet, set the fuel screw to 2 1/2- 3 turns out from seated & then ride it. Leaving the lid on even with a better pipe, you're not getting the full effect.

If you are using another jet manufacturer you'll have to ask around to what sizes are the best.