Different Jet Size Meanings...

[apalusso]

I was wondering what the different sizes of jets would be used for? Meaning, what would a 175 be used for in compared to a 145? My modifications that I have made: wb slip-on, k&n air filter, air box lid on. Everything else is stock.

The reason why I am asking, I recently bought 5 jets above the stock 400ex size and 2 below. But was wondering in what areas would I use these different jets? I would like to label them so that I will know if I am in a certain area I will know which jet should be used at that specific location.


Thanks for your help.
Aaron

[chrisp333]

hey man with the mods you have id trya 155 main or so prob your best bet depending on you elevation...

the others, i guess you could label them, but unless your doing stuff like changing pistons or cams yourself i wouldnt worry about it to much.

cant help on labeling, sorry

[cals400ex]

jetting is trial and error. it will be really hard to label jets. jetting is affected by temperature, humidity, altitude, and modifications made to your bike. labeling jets would be nearly impossible since your dealing with pilot jet, fuel skrew, main jet, needle taper, and needle clip position. you can guess what jets you will need when you change riding areas. when riding in winter, you will probally need to go up one size on your jets to compensate for the colder more dense air. a 175 jet would not be necessary unless you have internal motor mods. a 145 would not be used in a 400ex unless its very hot and you moved to a very high altitude. i have seen some people change jets due to riding conditions. for example, i have seen individuals put in a main jet one size too big (rich) if they are constantly running near full throttle since running them rich keeps it a little cooler. i agree, a 155 keihin main would probally suit you quite well for your modifications.