Jet needle question

[400EXBill]

Ok, first, here's my setup. I have an fmf slipon exhaust with a k&n airfilter. I have removed the airbox lid and replaced it with an outerwears prefilter. I have a 152 main jet and a 42 pilot jet. The guy behind the counter at the bike shop said to also move the clip down one notch on the jet needle to open this up a little bit more for better mid range performance. Is this a good idea? The reason I ask is because this is the first I've heard of doing this. Any help would be appreciated.

[ImWhite]

if its running fine leave it alone,if its lean i believe u would put it in a notch if its rich u would take it out?some1 else will correct me if im wrong,alot of people on here know alot more then me ;)

[400EXBill]

The only thing I have done to it so far is put the slipon exhaust and K&N and outerwears on it. I still need to put the new jets in before I run it. I figured I would do the jet needle at the same time if this was a good idea. As of right now, I have no idea how it is going to run. Figured I would ask on here before I do it.

[400exstud]

Yeah I am going to drop my needle this weekend because it is running lean.

I would change it if I were you and if you don't notice any difference leave it at the richer position because you are usually better off too rich than too lean.

I take it you know where the needle is. Just in case you don't, it is under the top plate on the carb. Pretty easy to change.

[Kuba]

Guys I am having some jetting issues as well.
04 TRX w everything stock except for yoshi exhaust and KN filter, airbox lid intact.
using dyno jet kit. I think this was a mistake because the jet sizes are to their own specs.
The needle is also different so things are out of wack a little.
I am running a main jet of 42 and will probably move down to 40.

The needle was originally set in the 3rd position as recommended by the instructions. It was running pretty rich in mid range so I changed it up to the 2nd position. Now it runs a little better in mid range but still a little rich, I am playing around with the adjustment screw.

I am now running a 142 main as recommended ( this is what I meant when the sizes are different), 42 pilot and 2 1/2 turns out. with the needle set at the 2nd notch from the top.



something is not quite right with full throttle, it is still smoking a little and I noticed last time a slight flame shot out the back .

has anyone had experience w the dyno jet kit, what are you running , I am in so cal and usually run at 1-3000 ft.

I really appreciate any help or info.

[hauck400ex]

I have a little more done to my bike, but wen i had a slip-on, k&n and no lid, I have a 170 dynojet with the needle on the 3rd clip down and my screw 2 1/2 turns out and she ran mint... Now i have a piston, cam and flywheel key and run a 195 and im on the 4th clip down and a 42 pilot... plug burns fine and have had no problems at all

[400EXBill]

Ok, now I'm wondering if I have the right main jet... Stock is 148 right? Is this a Dynojet number from the factory? Also, I bought the 152 jet at the Honda dealership I bought it at. I'm assuming they use the same numbering system as their manufacturing plant, right? Seems like you guys are runnin bigger mains than the one I have....

[hauck400ex]

dyno jets are different... the numbers dont match up at all the the dynojet ones are higher than the stock numbers... i use dynojet cause i got the whole kit for cheap...

[400EXBill]

So what brand compares to stock numbering? What brand does Honda use?

[underpowered]

honda uses stock Keihin jets, same brand as your carb. your 152 Dynojet is equal to like a 158 keihin. someone on here had a chart showinf exact crossovers between thw two. for just a pipe, filter and no box lid i would run like a 155, so your jetting if fairly close. with teh need clip moved down one and your current jetting i would say you are a little rich. try going down a size in the jet or raise the needle clip. To be sure, do a full throttle run then pull the plug right after, do not let it idle. for the plug check youwant a cocoa brown color. black is too rich, white or grey is too lean.

[rneal]

The factory jets are keihin and will have a K stamped into the side. The 400ex is a little lean as it comes from the factory, so bumping up the jetting is good even without major mods. With the lid off, aftermarket filter, and slip on exhaust the engine is breathing much easier. I would guess that the main will be somewhere between a 152-165.

Definately drop the needle clip one position, but watch out for the crappy brass screws that you have to remove to get to the needle.

I would also bump up your pilot to a 40 or 42. This is more to cure the winter starting issues. I run a 42 but that is a tad rich so I'm going to try a 40.

The best way to determine your jetting is to check your plug at each throttle position.

0 - 1/8 throttle = pilot
1/8 - 3/4 = needle
3/4 - wot = main

If you have any questions, shoot me a pm over at FTA. I go by Poky over there...

[400EXBill]

Cool! Thanks for the info. :)

[400exstud]

dyno jets are different... the numbers dont match up at all the the dynojet ones are higher than the stock numbers... i use dynojet cause i got the whole kit for cheap...

Nope DJ's are bigger than kiehins. Your over a 200K which should be on like a 505ex. HA:p