I need some help with jetting...

[Jesse400ex]

As some of you may know I recently rebuilt 06 400. 406cc Namura piston 11:1, stage two hot cam and HD cam chain, ground out welds, hmf slip on, K&N no airbox and dynojet kit.

I need some help jetting, the dynojet kit only goes to a 170 and that still dose not seem to be enough fuel. Still doesn’t sputter at WOT. I’m buying Keihin jets from jetsrus, but I don’t want to buy any jets I’m not going to use.

So if I’m running a 170 dynojet what size Keihin jets should I buy? From what I read 170 sounds rich, dose this sound unusual running that size of jets for my set up? I’m just wanting to get this back on the trails. Thanks

[honda400ex2003]

a 170 dj is pretty big in keihin stuff.

Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5



this is the full chart of them compared. a 170 dj is a 190 keihin. if i was a bertting man i would say around a 165 would be good. first thing to do though is get rid of the dj stuff. all of it, not just the jet. hte needle has to be changed too if it is a dj needle. find the stock stuff then you will have much better luck tuning. steve

[Jesse400ex]

I’m still running my stock needle, so if I’m running a 170 DJ I need to buy a 190 through a 210 is this correct? All I have changed in the carb is the main jet.

[honda400ex2003]

i suppose you would need those. how are you determining you are not rich enough yet? that seems way too big for any 406 to be running. just my .02 though. dont mix and match them anyway since it doesnt work too well together. steve

[JOHNDOE83]

This seems odd to me, Id think there was a secondary issue.

A 190 in a 406 like steve said is very strange.

[4reeds]

You have a dyno jet kit and you are only using the jet.Why would you not use the needle that comes with the kit?Have you tried the needle?If not, go back to the keihin jets. Thats one expensive jet if thats all you bought it for.

[Jesse400ex]

Everybody is wondering why I have not used the DJ needle, because everyone tells me its crap and not to use it. I have just used the main jets. How am I determining its not running rich, because I am running a 170 DJ main and it still dose not sputter at WOT. So I must still need more fuel, correct?

[4reeds]

The dj needle is tapered different then the stock needle.I used it in my 450r and it runs perfect.Some like it some don't.I had good results with it.Your bike will also blow smoke when you get on it if you are rich.Pull your plug and see if it is black,white,carmel color etc. That will help you with determining if you are rich or lean.

[Jesse400ex]

I guess I will pull the plug and carb back off tomorrow and see what the plug looks like. I did try 165 main and it started smoking a little when I got on it and when I changed gears. So that scared me a little and I haven’t drove it since. I thought if it was running rich it would stumble at wide open throttle and it almost runs out of power on the top end, but never stumbled on the top end.

[TRXRacer1]

I'm wondering if you don't have an intake leak. That's just a lot of jet there.

[Jesse400ex]

I will double check but I have looked, how would that relate to my problems?

[JOHNDOE83]

The air leak would cause you to suck more air from where ever the leak is, causing you to need more jet then normal.

Alot of times when the head comes apart for bores or whatever, sometimes a intake boot gasket is overlooked, bolts arent tightend enough, intakes crack...etc.

Some 416s, need anywhere from 170 to 190ish, 426s the same, 440s need 180 to 200s, so a 406 needing more then 190 is very odd.

I guess it could happen? But I doubt it, I would double check everything...IMO.

If everything checks out good? Then jet away, I just cant see a 406 needing that much jet?

[Jesse400ex]

Originally posted by JOHNDOE83
The air leak would cause you to suck more air from where ever the leak is, causing you to need more jet then normal.

Alot of times when the head comes apart for bores or whatever, sometimes a intake boot gasket is overlooked, bolts arent tightend enough, intakes crack...etc.

Some 416s, need anywhere from 170 to 190ish, 426s the same, 440s need 180 to 200s, so a 406 needing more then 190 is very odd.

I guess it could happen? But I doubt it, I would double check everything...IMO.

If everything checks out good? Then jet away, I just cant see a 406 needing that much jet?

Trust me, I thought the same thing.

[Jesse400ex]

I pulled the plug and carburetor, the plug had hardly any color on it. I pulled the needle and it wasn’t adjustable so I put the dynojet needle in it. I held both of them together with the DJ needle on the 3rd groove and it was slightly shorter than stock.

So I set it on the fourth notch on the needle. I drove it a bit up and down the road and seemed to run well. I did notice when it was warming up idling I would hit the throttle WOT and would sputter and sometimes die. While at the same time I saw a small bit of white smoke.

After driving it I pulled the plug, it looked a light brown tanish color. I was thinking about takeing the needle back out and putting it on the third groove, but since its shorter than stock I would run leaner than before, correct? Am I getting any closer, or do I still need to buy more jets? Its hard to emagine I need to go bigger than a 190 main. Any advice?

[4reeds]

I would say you are close.Move one notch and see what happeneds.I think you are close.Turn your f/s to 3or 3 1/4 turns seeif that helps the bottom end.light brown is good.put it on the third notch.good luck

[JOHNDOE83]

You CANNOT just pull the plug and look at it, thats not how you read a plug and not how to determine jetting.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=plug+reading

[4reeds]

Originally posted by JOHNDOE83
You CANNOT just pull the plug and look at it, thats not how you read a plug and not how to determine jetting.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=plug+reading No one said its how you determine jetting.It does help with figuring out if your rich or lean.

[TRXRacer1]

Originally posted by JOHNDOE83


Some 416s, need anywhere from 170 to 190ish, 426s the same, 440s need 180 to 200s, so a 406 needing more then 190 is very odd.

Bore size has next to nothing to do with jetting. It's all the other work done that matters. This is horrible and confusing advice to a newb.

Also nobody should be jetting by the look of their plug whether it's "chopped" or not. I do agree however with 4 reeds that seeing a light brown plug can be an indicator that your jetting is at least on the right course.

[Jesse400ex]

If the DJ needle is set on the third notch and held up beside the factory needle, the DJ is actually a little shorter than stock. So if I move it up on the third notch wont that make it leaner than stock?

[4reeds]

nope,it allows more feul to pass by.This makes it richer.Closer the needle is to the jet the less feul.

[Jesse400ex]

so going up on the notch of the needle, the richer it is?

[dalejiw25]

Steve has already given you the Best answer.

"first thing to do though is get rid of the dj stuff. all of it, not just the jet. hte needle has to be changed too if it is a dj needle. find the stock stuff then you will have much better luck tuning. steve"

[4reeds]

The further up you go on notches the lower the tip of the needle will be toward the jet.This will make it leaner.The lower you go on the notches,towards the tip, the richer it will get.

[honda400ex2003]

do yourself a favor and get the stuff. you can try all you want. you can even get mad and threaten your machine lol. I know, i was there not long ago with mixing and matching. once you get the stock stuff it will be good. the dj stuff is better for the ethanol setups that need more adjustment. keep the dj stuff for that. steve

[Jesse400ex]

First off, the stock needle on mine is Not adjustable. I used the DJ main jet out of the kit I have purchased before I knew I would have any of these problems. Then someone on here said to go ahead and put in the DJ needle to see if it would help it. Now they say just throw all of it away. Well I don’t exactly have money to throw away, so I was trying to make this work with what I have. I didn’t want to spend another 40 buck on jets if I could make these work, that’s all. Thanks for the Help!

[honda400ex2003]

alrighty then, go with a 152 dj(if you have one) or a 155, 2nd clip position from top on the dj needle, 3.5 turns out on the f/a screw and see how it does. that will be about as good as you will get it to run with the dj stuff. the dj stuff is not made for bigger stuff, it works great with an exhaust and filter but when you need to start getting more gas to it, they dont work very well. the needle doesnt go into the correct position. maybe a .030" shim would do it. you could go to the 2nd on the needle then shim it to see if that gets it about right. it will be just less than 3 but more than 2. may be the correct spot to have it at. if you have your stock needle, check it to see how it looks for length wise and such while you are at it. new jets for your stock needle would be about 15 dollars. I would almost guarantee that you will not have to move your stock needle too far if at all. you could shim it but that would probably make it worse with the stocker since it is in the 3rd position already. if you shimmed it you would almost be to the 4th. steve

[Jesse400ex]

Thanks for the info, I will try to tinker with it tomorow.

[honda400ex2003]

well... good luck! you will need it lol steve