Jetting and reading plug- help

[Pur Pony]

Ok- just installed a yopshimura race pipe/header on my '01 400ex. Im also going to have a K&N and vented airbox. I talked to a few guys on here and they recommend using a 155 or 160 main jet.
Yoshimura e-mailed me saying 2 steps up on main(148 factory)- so that should put me around a 152 main jet correct???

also... do I have to change my SLOW jet and or my SLOW AIR jet??

Someone said on here to run a 40pj??? what is that?? Im guessing a larger SLOW jet??

and how do I change the setting on my needle groove- YOSHIMURA says #2 on the needle groove?

last of all... how do you read a plug??

After changing jets how far or how long to you run it before taking a plug reading?? and should this be tested using a NEW plug or the plug thats been in since i got the machine?

thanks for all the help- im new to playing with bike carbs-.. well really any carbs-
im a EFI guy- lol

thanks much

[riz400]

Here is a site that will answer most of your questions. Go to the tech center and click on Carb Jetting.http://www.duncanracing.com/

If I were you I would go up two sizes on the main, one size up on the pilot(if it is still stock size) and see how she feels. If she feels sluggish drop down one size. Whatever you do don't do anything drastic and make one change at a time.