i just bought a ct pipe and rejetted to a 155 and my z will not idle it pops and sputters i also tried a 147 what em i doing wrong or do i need to go smaller or bigger also i have not messed witht he needle do i need to do this any information would help thanks

 

Did you mod the airboz at all?(take lid off, put holes in it)

 

I went and checked into your problem. With the pipe only with stock filter you should be running a 155 according to CT. With your K&N you need to go up a size or two. If your not running your airbox lid then you need more. 160 with K&N and the lid installed 165 with no lid.

 

thanks i will try putting in a 160 today thank for the help

 

According to the DynoJet trouble shooting guide, your bike can idle without the main jet if set up properly. The idle circuit is separate from the main jet circuits. If you added a pipe, your bike is probably breathing a lot better and running real lean, thus the backfiring (popping).

Try turning the idle mixture screw out (counter-clockwise) a half a turn and see if that helps. That will richen the air/fuel mixture.
Better yet, go down to Sears and buy a tachometer or multimeter with a tach and set your idle mixture and idle speed with it.

Here is how I set up my Vinsons and King Quad ATVs. If you choose to follow what I do, you do so at your own risk. I don't want to be blamed if anything goes wrong.

Here's what I do:
Make sure you start with an engine that is warmed up. Then hook up the tach. Set the idle speed to spec with the idle speed screw. Then turn the idle mixture screw slowly until the tach shows the RPM has peaked. You may need to go either direction (clockwise or counter-clockwise) to find the RPM peak. The idle mixsture screw setting where the RPM peaks is the optimal air/fuel idle mixture for your altitude. After you've found it, go back and with the idle speed screw, reset the idle speed to spec.

Get your idle problems solved first before you start changing main jets.

Hope this helps.
Mark

 

MARKS RIGHT; MAIN JET HAS NOTHING AT ALL TO DO WITH IDLE

 

I have a z with a white brothers r4 exaust and pro flow adapter with a kn filter and tryed to use a 160 main jet that come with the exaust and it just would not run good . It would hesitate and pop at high speeds, I removed the air box lid and ran like a champ but I don't feel comfortable running with out it due th my riding conditions and I want my engine to last.Do you guys think rimoving the lid hurts the engine at and do you know what I could do to keep the 160 in, because you sure could tell a difference in the power with in on there.

 

According to Neal at CFM the Z400/KFX is fine without a lid. The fendors protect the box very well. Only time there would be a problem is if you run the bike in very deep water. So depending on your riding conditions should be your final decision. If your like me and run in sand and mud and shallow water all the time running without a lid woln't be a problem.