ATV Florida Forum

i'm rejetting my neighbors z400.
yoshi told him to leave the idle jet and to only change the high rpm jet from a 130 to a 148. i changed the needle and adjusted it up to only one notch from the bottom(hence raising it) the exhaust still gets red at idle and when i accelerate it, it gets more red.

question:

1. does raising the needle make it more rich or lean.
2. should i put a bigger high rpm jet or will putting a bigger idle jet also affect full throttle.

thanks for the help.

PLEASE help. thanks, gery

you are way lean, are you what size pilot jet are you running? the needle I would suggest the 4th clip down, raising the needle allow for more fuel at part thottle. you'll want to try and jet the carb around the idle screw being 1.5 turns out. any more than that and it is not right. you might want to look into the jet4power system I run it on my YFZ and love it

chuck, should i put a bigger idle and high rpm jet.
will changing the idle jet increase the overall air fuel ratio or only idle mixture?

also what do you suggest  i'm at 146 now, should i go to a 150 or a 155?

Do you have the air box lid on or off? Have you messed with the snorkel?

actually the lid was off when it was going cherry red.
would  a "lid off" condition affect  the mixture that much?

yes, because you are allowing alot more air in than usual

1. Moving the clip down towards the sharp end of the needle richens your mixture from 1/4 to 3/4 throttle.
2. Idle jets are only for up to 1/4 throttle and have no affect on full throttle.

If you are lean on your idle jet after you let off the gas you rpms will "hang" for a second then it should drop down to idle. If that happens go up one size on your idle.  Typcially for just a pipe change you would really only need to change the main jet. But if you did the air box lid and a pipe  you main need to go up one more main size and move the clip on the needle down one notch. But removing the air box lid will give you more air throughout the whole rpm band, hence the bigger idle jet, moving the clip, bigger main. 

-Mark

The jetting you mentioned would probably work well with the lid on. I'm not real familiar with the Z400 but I would guess that you need like a 180-200 for an open air box. Try checking out www.z400central.com

awesome guys. i really appreciate your help.
last question ..................

i'm guessing under no circumstance should that pipe be cherry red, right.

nope. especially cherry red

it is normal for a pipe to glow red. you will see it more at night. the pipe can get 800 to 1100 degrees. its going to glow. if its a new pipe it will do it at first. if you hit the throttle and it comes right back down ti idle, its fine. the raptor we put pipes on always turned red

You are correct. You should only be able to see it glow at night not during the day.

I guess I should have been a little more clear.