PDA

View Full Version : What size Jets?


tman12345
03-08-2008, 01:41 PM
I plan on purchasing a HMF sport slip on soon and I'm not sure what size jets to use. I'm complete noob to jetting so.... anyway its a 2003 400ex with a K&N filter, outerwear pre filter and the airbox lid is removed. Currently its got a supertrapp exhaust with a 178 main jet. If theres anything else one would need to know just tell me. So what size jets would you reccomend.
tman12345
03-08-2008, 02:05 PM
oh yeah its going to have a quiet core too.
BigBore24
03-08-2008, 09:34 PM
is that a keihn 178 main? cuz that seems really high with stock bore
tman12345
03-09-2008, 09:20 AM
Originally posted by BigBore24
is that a keihn 178 main? cuz that seems really high with stock bore

I was told when I got it it was a 416 but there was no paperwork for that. I recently brought it to a shop for some work and the guy who works there put in the 178. Does that sound right?
BigBore24
03-09-2008, 02:09 PM
that sounds a little more reasonable for a 416. if all you are doing is changing out pipes you should be pretty close already. do you know what you are on the pilot jet? i would buy a couple sizes in each direction on the main and a 40 and a 42 on the pilot (if it is a stock 38 now) and just plug and play. it will take some time but its really the only way in my opinion. there are just too many variables to know exactly and get it perfect the first time. pay attention to how it pulls throughout the throttle spectrum and how quickly it raps up. they say checking the plug doesnt really tell you anything anymore cuz of the additives in gas, but its not a bad idea to pull it after you get it close and been riding a while to see what shape its in
tman12345
03-09-2008, 03:32 PM
Originally posted by BigBore24
that sounds a little more reasonable for a 416. if all you are doing is changing out pipes you should be pretty close already. do you know what you are on the pilot jet? i would buy a couple sizes in each direction on the main and a 40 and a 42 on the pilot (if it is a stock 38 now) and just plug and play. it will take some time but its really the only way in my opinion. there are just too many variables to know exactly and get it perfect the first time. pay attention to how it pulls throughout the throttle spectrum and how quickly it raps up. they say checking the plug doesnt really tell you anything anymore cuz of the additives in gas, but its not a bad idea to pull it after you get it close and been riding a while to see what shape its in

alright I'll do that, but where is a good place to buy jets?
BigBore24
03-09-2008, 03:53 PM
your local honda dealer or jetsrus.com
tman12345
03-10-2008, 01:52 PM
also is there some way to figure out the size of the jets already on if you don't know? Is there like an engraving or something?
Brauap
03-10-2008, 02:07 PM
I got mine from JetsRUs, and I love them. Thats where I am going to buy the from now on. Very fast shipping, and it comes with a sticker!!!!!!!!! I love stickers.. :blah:
Brauap
03-10-2008, 02:08 PM
About knowing what size it is, yes it says on the side. Just look and you'll find it. its pretty small though. But its a nice feature to have!