Starting Point On Jet

[hjsmith00843]

Here are my upgrades that I will have to the motor after I finish next week.

This is what I started with.
Stock piston, cam, muffler and a K&N filter with open top

I am adding these parts.

11.1 wesico piston
stage 2 magnum Cam
Sparks Key
Lexx MXe Slip-On Silencer With Mid-Pipe
Mild Port Job
Gonna Grind out the exhaust header
Remove the choke
Gonna run a mix of 110 race fuel and 93 octane

My orginal jets were 160 and 38

How much performance will it gain. Will it be very noticable. Remember this is my first atv and I already thought it was super fast.

Later will add a CDI Box, performance coil, 450r carb.

are these parts worth getting
Spark ampifier




also what kind of impr

[honda400ex2003]

it should be a totally different machine. What bore are you going with? We will need that along with your elevation to give you an estimate on jetting. steve

[hjsmith00843]

It is a stock 85mm. My elevation is at or just above sea level.

[honda400ex2003]

i would start with a 170 then, it will be a bit on the rich side most likely, get a 42 pilot and put in at 2.5 turns out on the f/a and see how it does. I would venture to guess it will be around a 168 or maybe 165 when finished. I say a 170 since you are at sea level and it will help to start out rich then work your way down instead of starting down and going up. It is a worry to break in a motor with it lean. :eek2: It makes me nervous anyway lol. steve

[Wr3sTl3b0y]

hey any chance you could help me
1000 feet above sea level
K&n filter
no top lid
outerwear pre filter
e series muffler with baffels little leak
stock header
stage 2 hotcam camshaft
440 big bore 89 mm 11:1 i belive

running a 42 pilot didnt try it waiting for a starter just downsized
172 main

when you barely touch the throttle just a weee bit it coughs doesn't eel like it should have the power with the upgrades i got barely stand it up in second gear trying hard 2 turns out on the f/a screw

[honda400ex2003]

you are gonna need bigger than a 172 i would say. I would go to about 2.5 turns out on the f/a screw with the 42 in it and see if it helps with the cough just off idle. put the needle on the 3rd notch for now, and i would say at least a 180 to start if not a 190. I am not really sure on what the 440 guys are running. steve

[hjsmith00843]

I just ordered a 165 168 170 172 and a 42 pilot jet. Should I need anymore to tune this thing in?

[honda400ex2003]

imo you shouldnt that should give you plenty to choose from. steve

[Wr3sTl3b0y]

190 man breakin my balls haha biggest i got is a 180 and im pretty sure that didnt run right it chocked out when i stomped on it and as for the notch i havnt exactly found that yet i know under the main theirs a nut to turn up and down when tightening ill try it all out only have 1 day to work on it before the race and i dont wana blow it up

[honda400ex2003]

do a quick search on 440ex jetting and see what some guys are running, I really am not sure how big you will need. I have seen guys with 190s in them lol. With the smaller stuff it is easy enough to take a decent guess since you can kind of compare between stock and a 416 and such. I dont have any experience with the 440s to know how the ratios looks air wise. With the stock bore and exhaust it is around a 155. A 416 with that exhaust and everything done is around a 170. anything in between is pretty easy to take a stab at lol. Too many variables to guess it completely correct for any given machine. steve

[Wr3sTl3b0y]

ill give it a whirl if i get a chance i just got a new starter coming like i said mine was fried so i couldn't really get much testing done with the jets and i c 440s running with 220 mains but they got a few more upgrades to the head and stuff

[hjsmith00843]

Once I get the motor togather how do I break tne new piston and rings in?

I am gonna start with the 170 jet. Want to make sure I dont get it too hot on the break in. Just want to make sure that the rings seat well.

[honda400ex2003]

This is a tough topic now, people have their own way of breaking in a motor. I for one, when i did mine this last time took 3-4 15 minute practice track type sessions with a good cool inbetween each of them. I was on and off the gas in lower gears to help build pressure in the combustion chamber and help to seal them up good. others like to ride them easy for the first tank or so. you will feel it as it starts to seal up nice and tight cause it will just keep getting better and better. lol. steve

[88dunerider]

how far out are you running the nut above the main?or i should say how much are you letting the main sit down in the bowl

[hjsmith00843]

Originally posted by 88dunerider
how far out are you running the nut above the main?or i should say how much are you letting the main sit down in the bowl

to be honest I have no clue what you are refeering to. Please let me know so I can check it out.

[fasterblaster09]

I need a little help also lol. Ok I just got a 2002 400ex, has supertrapp shorty slip on, cam, bored to 416, 450r carb. It pops on decel. He said now it is 205, 52. What do yall suggest?

[88dunerider]

the part you srew the main jet into , it also un srcrews out of the carb and there is a nut on it to determine how far you screw it into the carb and depending on how far you have the nut on the mysterious part is how far the main jet sits down in the bowl and fuel.

[88dunerider]

oh and fasterblaster, im still trying to figure out my jetting also but the popping on decel means its to lean , i would take out the main just to see what it really is , i was told the same thing took mine out and was like 20 jets smaller , so take out the main and make sure the pilot is a 52

[hjsmith00843]

Ohh ok. We change those around a little in kart racing too. It is called a e-tube. Emulison tube. It is what mixes that air/fuel togather inside of the carb. The goal of it is to make the fuel frothy with air.

Well in kart racing that what it does. I am not sure on the atv's yet.

[honda400ex2003]

:rolleyes: :rolleyes: :rolleyes: :eek2: oh god. just make sure everything is tightened and dont start messing with how far out mains sit and such. leave the bigger shaft alone. Just put the jet on the end and leave it at that. Popping on decel means you are too lean put the 52 in and go to 2.5 turns out. THE MAIN JET DOES NOT AFFECT THE PILOT CIRCUIT AT ALL!!!!!! no matter what you do to the main it will not richen it up and make it quit popping or anything. go run it wide open for 30 seconds, kill it and pull in the clutch simultaneously. SEARCH PLUG CHOP and read about how to do it. this works on any of the 3 CIRCUITS but running the machine at that throttle range. All three of you guys are just going at this the wrong way it sounds like. faster go with my setting for my 450 CARB not the 400ex carb and see where it gets you. you shouldnt need a 205 in a 416 unless you have a major air breather. Do you have your lid on or off, no air box at all? steve

[hjsmith00843]

ohh I am not going to play around with the e tube in anyway or leave the jets loose. Not like we are looking for every .0001 of a HP.

Thank everyone so much for the information and help given so far. I ask alot of questions and read alot. I have been sick all night and could not sleep.

I started from a year out and browsed through all of th e400ex threads. So much can be learned on these forums.

I still have about 30 pages to look through.

[honda400ex2003]

Nice get well, i noticed you have an ear infection that sucks. I think all of the newer members should do just that. most of the questions that could possibly be asked can be found for sure in the last year if not the last couple of months. good luck with your machine. make sure you read up on doing some chops, it is not the best method but it is better than just getting on it and going for a sunday stroll around the yard for 5 minutes then being like, hey it is too lean ill go up when in all actuality it could be too rich on the main but lean in the needle or on the pilot. lol. steve

[hjsmith00843]

Hopefully by next weekend I will have her going again. Lots of parts are on the way for the motor.

Just placed my order for the slip on and the jets.

After the break in I will do alot of plug chops and place pictures of the plugs up so maybe get some good readings.

Saw a few other mods that I want to do just by searching. Like

Removing the resistor from the plug wire

Installing a new hood and doing away with the lights.

I might be getting into hare scambles when I get more riding experiance. I have a full size track that I am allowed to practice on when ever I want to just about a mile from my home.

I am going to have so much fun with atv's. Wish I would of started running them instead of kart racing.