Has anyone played around with taking the snorkel cover or airbox lid off? If so do you have jet sizes as a starting point? My Z400 is a really great quad and we will be racing it very soon. Middo

 

I'm useing a 140 and I'm at 5000ft. If your at sea level to 1000ft try a 155....

 

What is the stock size of the main jet. I am going to put a K&N filter on mine and take off the snorkle, will two jet sizes be adequate. I am at about sealevel and no other mods.

By the way Sandgod I took your advise and bought the Z400 and could not be happier.
Thanks

 

Hey Coolhuh, where do you live? I'm right next to Rogers HS, on a cul-de-sac full of quadriders.

The stock main jet is 130. I replaced mine with a 150, but it probably needs a 152.5 or 155.

 

You have to go from .130 to .152.5 just to remove the lid? Seems like a lot if we're only getting 2 hp or so.
I think I'll order my stuff tomorrow. [img]i/expressions/face-icon-small-smile.gif[/img]

 

I tried it w/ no lid, and it ran like crap.

I is obvious that a jet swap is in order.

Is a 155 needed for just the lid??

What about when a pipe and air cleaner goes on???

LOBE
~~~~~

 

My Z is still stock, and I'm seeing a lot of black soot in the muffler (removed the end cap to see if I could remove the baffle). Looks to be running rich. If I remove the snorkel and/or airbox lid, should I need to increase the main jet??

 

If you pop the lid off w/o a rejet the quad will fall on it's face....Always bump up at least .5 after putting on a K&N filter also no matter what was done before...My end cap is off, no lid and the top piece removed off the snorkel, but the snorkel is still on...

 

Lateapex,
I live in the downtown area by the sounder station.

 

If you look at the Yoshimura dyno charts, you'll see 150 is the minimum for mods to our engine. Suzuki has done a marvelous job tuning the 400, as it has great performance with an emissions-friendly carburetor and relatively small main jet. I suspect the small main also contributes to good fuel economy. All of which underscores the scope of effort required to produce a first-class atv.