Confirm jetting

[chiaml]

I think i have a good idea of how to initially jet my '05 400ex, but I think i'd like to hear it from someone else.
Totally stock bike that i'm adding a uni filter and full yosh rs3 system to. I'm at sea level. Temp now is in the 40's.
I was thinking moving the needle clip to the third groove
Using a dynojet 146 main jet
Turn the fuel mixture screw 3.5 turns out.
This sound like it'd get me close to the mark?
Would things change when summer comes and it' 80/90?
Any input would be appreciated.

[Honda#4]

you would be running richer when it gets hotter so you would have to run a smaller main jet. The only way I can explain your problem in more detail is for you to run it like that and see what it's doing, like popping or backfiring on decel= lean or sputtering and bogginging down= rich. Hope I have my wording right if not someone correct me.

[AbnMP13]

I ordered a K&N lid for my airbox so I'll soon be trying to rejet mine. I'm keeping an eye on this thread to see if I can gain some knowledge also.

[chiaml]

I would prefer to jet it for warmer weather. I hardly ride in the winter and do most of my trail riding when it's warmer out. What main jet would you recommend then? Or should i just change my fuel screw?

[MO-EX-RIDER]

i have close to the same mods only modded air box and slip-on. i had a 165 DJ and 3 turns out on the screw clip on 3rd notch and was close, but on the rich side(dark tan/black on the plug) the 146DJ is way to lean...start with the 155 and go from there

[chiaml]

thanks for sharing your experience MO.
I think i'll start with the 155 and 3rd clip down on the needle.
I also wanted to try a 40 pilot jet to help with starting.
Are Dynojet main jet sizing the same as keihen?

[Honda#4]

Do you want to run with or without the lid? What size is your pilot? Try a 160 main and put the clip on the 4 grove from the top without the lid.

[chiaml]

Honda#4,
Currently, it's completely stock, so i'm not sure what my pilot is (assuming 38). I'm running the stock lid on as i do alot of trail riding which sometimes involves semi-deep water. What do you suggest?

[chiaml]

Btw, what is the stock main jet and stock pilot jet. Just so i can understand a little better how much this is moving up.

[Honda#4]

Stock pilot is 38 and main is 148. Put in a 42 pilot that will take out all the cold starting issues if any, try a 155 main with the clip on the 3rd or 4th notch from the top should be pretty close. Any more questions just ask.

[Eviltanker]

On mine I am Running a 150 and a 40, bought a keihen adjustable needle and put it at 3rd notch. don't know why but it seems mine didn't have to go up too much to get perfect. BTW I'm running all Keihen Jets. Mods in the Sig.

[Honda#4]

It's probably cus of your altitude.

[GPracer2500]

Originally posted by chiaml
....Are Dynojet main jet sizing the same as keihen?

NO. They use a different scale (i.e. K155 ≠ DJ155).

[AbnMP13]

Originally posted by Honda#4
Stock pilot is 38 and main is 148. Put in a 42 pilot that will take out all the cold starting issues if any, try a 155 main with the clip on the 3rd or 4th notch from the top should be pretty close. Any more questions just ask.

So the pilot is the reason mine's so hard to start cold?

[hornetgod13]

Originally posted by AbnMP13
So the pilot is the reason mine's so hard to start cold?

These quads are notorious for cold stating issues. The Pilot jet will cure the problem. Once I installed a #42K Pilot. My 400EX didn't even need to be choked in cold weather. Just pump the throttle a couple times and it fires right up.

[chiaml]

GP...is there a way to figure out the conversion. The reason i got the dynojet kit was for the adjustable needle. Maybe there is a better way out there, but now i have what i have. Any ideas on how to figure the conversion?

[Honda#4]

Yes AbnMP13 that's the reson just put in a 42 pilot and that will solve your problem.

[GPracer2500]

Originally posted by chiaml
GP...is there a way to figure out the conversion. The reason i got the dynojet kit was for the adjustable needle. Maybe there is a better way out there, but now i have what i have. Any ideas on how to figure the conversion?

From Dynojet:


We are often asked for a "cross reference" sheet that compares our main jets to Mikuni or Keihin. The fact is you cannot directly interchange the jets for a given size. Many things affect fuel flow through a jet of the same orifice size. The entry and exit tapers of our main jets differ from those of other companies. Due to this, the fuel flow changes as a function of velocity through the carburetor venturie. This means that two jets of equal orifice size will have a different fuel flow curve relative to intake air speed. At a certain speed the two may flow equally, but a change in velocity changes the flow characteristics. The Dynojet main jet hole size is measured in millimeters. For example, a DJ142 has a 1.42mm hole.


Michael Cory
Research & Development
Phone: 800-992-4993 EXT. xxx
Michael@Dynojetxxxxxxxx

Dynojet is absolutely correct about the shape of the hole influencing flow characteristics. No smoke and mirror techno-babble there. Nonetheless, there's this chart. It is based on actual measured orifice size.

Dynojets numbers are simply the hole diameter. A 140DJ main has a 1.40mm (0.055") diameter hole in it at the threaded end. A Mikuni 140 has a 140 cc's of fuel flow per minute. I don't know where the Keihin scale comes from.

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

I think the chart is fine to use to get you in the ballpark. However once you start zeroing in on the correct jetting specs, you should be basing your jetting changes based on what the bike is telling you--not what someone else (who isn't testing with you) says is right for your bike/situation.

Good jetting skills start out with a basic understanding of the fundamentals. Next comes testing--lots of trial and error. Eventually you'll hone your skill on picking up those little signs indicating rich/lean. If you take the time to make incremental steps with one circuit until you're too rich/lean then you'll begin to learn what to look for. Knowing a few testing shortcuts here and there helps too.

IME, many folks don't have the patience to go through those learning steps. I'm not bashing--I understand that sentiment. There's nothing wrong with just wanting it to be RIGHT and not really caring about how it got that way. The trouble is, there are few shortcuts to getting jetting RIGHT.

$0.02

[hornetgod13]

I had a Dynojet kit installed but, got frustrated because the Keihin and DynoJet sizes didn't match and I was not a fan of the Dynojet adapter. I'm not even certain that the conversion chart is accurate either. That chart has floating around the website for years and I'm not even sure where it originated.
I eventually removed the Dynojet Kit except for the adjustable needle (I liked the adjustable needle) and went with keihin jets. I can buy individual keihin jets at www.jetsrus.com and it's easier to share jetting specs between riders. Most people use Keihin jets.

[mr.stinkyfinger]

Well I'm about to make a few changes to mine, any help would be appreciated. I have a 2004 400ex the mods will be HMF slip on, Power Bomb header from FMF, Uni filter, also added a WB rev box. Will have mod air filter box lid too, will be open with a outerwears cover. Thanks.

[Honda#4]

Stinkyfinger try a 160 main and the clip in the 3rd grove from top.

[hornetgod13]

I have all those mods with the exception in the Header and Rev Box. I run a 158K Main Jet, 42K Pilot Jet, DynoJet Needle on 3rd slot from top and fuel screw 2 1/2 turns out from lightly seated. My riding altitude is between 250 to 500 ft ASL and temperature is between 50 and 80 degrees (California) I just did a plug check today and it was a perfect light brown. I've been fine tuning my jetting for a couple weeks now and was very pleased to finally see I had it spot on.
A 160K Main Jet would be a good start for you. Put a new spark plug in and check it out.

[04exking]

This is a great post thanks for the knowledge.

[fullysic 400]

Hiya all,just my 2c worth,I run a dynojet kit,

146 main
needle on 3rd slot.
mixture screw 3 1/2 turns out.
K & N filter,no airbox lid.
modified exhaust
pilot left as standard.
current ambient temp 40-50 celsius
365m above sea level.
starts and runs like a dream,very impressed.no popping or bogging at all.

[AbnMP13]

I got a K&N airbox lid on the way, will soon be adding a full pipe (the wife don't know, anyone got an empty couch?) and am looking at a Moose CDI box.

Everyone talking about "clip on 3rd groove" and etc are referring to an adjustable needle?

[Honda#4]

Yes an ajustable needle

[hornetgod13]

Originally posted by AbnMP13
I got a K&N airbox lid on the way, will soon be adding a full pipe (the wife don't know, anyone got an empty couch?) and am looking at a Moose CDI box.

Everyone talking about "clip on 3rd groove" and etc are referring to an adjustable needle?

The higher you have the clip on the needle the leaner the setting the lower you have it (towards the pointy end the richer the setting. Most people I've heard on the website have there's set to the third slot down from the top.
Remember, there is a small washer that goes on top of the needle clip once it's installed back in the carb.

[mr.stinkyfinger]

Thank you for all the info. I'll give it a try this weekend and see how it does.

[AbnMP13]

The K&N lid came with a 168 and 170 main jet but no adjustable needle PLUS the local Honda shop is closed for inventory, gonna try going to the Kawi shop to see what they have. :mad:

[hornetgod13]

1.) www.jetsrus.com has a carb rebuild kit for the 400ex that includes a adjustable needle as well as several other items including a fuel screw, not sure if it's "D" shaped or straight slot. You would have to call to check. It cost about $27.00

2.) If you could wait, you can order a stock adjustable needle for a 1999 to 2004 carb (it will fir yours too) from www.servicehonda.com
NEEDLE JET 16012-HN1-003 $24.54

3.) DynoJet sells a Jet kit that includes an adjustable needle, 10 various sized jets, a DynoJet adapter, and a "D" shaped fuel screw tool. You will end up needing that tool to adjust your fuel screw if you have a 2005 or newer 400ex The kit cost around $50.00 but, I would only use the needle and tool out of the kit and stick with Kiehin jets.

Option one is the cheapest if the fuel screw is a straight slot. Some people replace the "D" shaped fuel screw with an older style straight slot or just cut a slot in it so it's adjustable with a small screw driver. That's just my 2 Cents.

[AbnMP13]

I'm gonna put a slot in that screw if I can ever get it out, or replace the screw if that's an option. $50 isn't really that bad for a tool and the adjustable needle, the needle is $25 by itself.

Then I can order a set of main Keihin jets over the internet for $25 for 5 jets. But what sizes should I order? I have a 06 400EX and will be adding a full pipe before summer, I already have the K&N lid and any other major engine modifications will be a year or so down the road. Thanks in advance.

[hornetgod13]

155K, 158K, 160K 162K, and 165K

Start with the 158K and do a plug check.

[chiaml]

How does tempreature play a roll in jetting? If i jet it today, when it's in the 50's, and then i ride it in the summmer when it's in the 90's...how does that play a roll?

[AbnMP13]

:D Thanks Hornet. Ordering them Tuesday.

I have a 155 in with the KandN lid and it seems to be running fine, no backfires, starts fine, etc.

[hornetgod13]

Originally posted by chiaml
How does tempreature play a roll in jetting? If i jet it today, when it's in the 50's, and then i ride it in the summmer when it's in the 90's...how does that play a roll?

Great question!
If you jet your quad for the winter months and it's 40 or 50 degrees outside than the air is thicker. When in the summer and it's up in the 90's than the air is thinner and the quad will be running rich(too much fuel) Typically going up or down one jet size is all you'll have to do between summer and winter months.

[chiaml]

I think i have a pretty good understanding now of the three circuits. Does the air/fuel screw just really dial it in the last bit. Say, you have the right main jet but need to fine tune the jetting?

[hornetgod13]

The fuel screw controls the fuel/air mixture for the pilot curcuit. If your quad is popping or back firing at low idle settings than it's lean and you need to turn the fuel screw "OUT". If the quad bogs than it's most likely rich and the screw needs turned "IN". This is only for low throttle settings from idle to 1/8th throttle. If adjusting the fuel screw doesn't cure you idling or 1/8th throttle problems than you may have to go up or down in your pilot jet size.
The Needle control 1/8th throttle to 3/4 throttle and the Main Jet control 3/4 to Wide Open Throttle.

[AbnMP13]

Originally posted by Honda#4
Do you want to run with or without the lid? What size is your pilot? Try a 160 main and put the clip on the 4 grove from the top without the lid.

Went to my local shop and bought an assortment of jets, asked about the adjustable needle and the parts guy told me I already had one in the bike, argued with him momentarily, then went to speak with the service guy, he confirmed what I knew and said the 05 and 06 models don't have the adjustable needle.

Any suggestions on where I can purchase one WITHOUT buying a entire jet kit?

[AbnMP13]

Originally posted by hornetgod13


2.) If you could wait, you can order a stock adjustable needle for a 1999 to 2004 carb (it will fir yours too) from www.servicehonda.com
NEEDLE JET 16012-HN1-003 $24.54



Not according to the local service tech, he looked it up and even the carbs have different part numbers.

[hornetgod13]

It WILL fit. The carbs have different part numbers because they have different fuel screw shapes and different fuel needles. Other than that the carbs are the same. The parts are interchangable. Those 2 parts can be swapped between the 2 carbs. You can use a 1999 to 2004 needle in a 2005 and up carb. I'm not sure why you even went to a local honda "Tech". Most of them don't know there @$$ from a hole in the ground. Just order the part yourself at www.servicehonda.com NEEDLE JET 16012-HN1-003 $24.54 or order a dynojet kit. That kit comes with an ajustable needle, "D" shaped fuel screw, a dynojet adapter, and 10 various sized jets. I'm not a fan of DynoJets but, I use the adjustable needle and fuel screw tool and stuck with using keihin pilot and main jets.

[AbnMP13]

He GAVE me a tool for the fuel screw and I bought the jets you recommended from them. (I also ordered an exhaust)

I'll order the needle tonight. How long does it take to order something from those folks?

Thanks again for the help.

[hornetgod13]

How much was the fuel screw tool? "GAVE" Does that mean it was free?
What exhaust did you order?
I've never ordered from www.servicehonda.com but, they are the cheapest at selling stock parts. You may have to call to order it.
I have ordered stock parts from www.bikebandit.com they usually costs a couple dollars more but they have excellent customer service, fast shipping and ordering is done online.
If you do order it through www.servicehonda.com let me know how it goes. I may start ordering from them.

[GPracer2500]

I've ordered from SH many times. I think they have a $9.00 min shipping charge now so bear that in mind for small orders.

I'll keep ordering from then. They always have the lowest prices and shipping times are reasonable (usually a week). I place my orders online and that works well. I have called them too and was satisfied with the service.

[AbnMP13]

Originally posted by hornetgod13
How much was the fuel screw tool? "GAVE" Does that mean it was free?
Yes, he had two or three of the ones that come in jet kits.


Originally posted by hornetgod13 What exhaust did you order?
HMF Ballance full system


Originally posted by hornetgod13 I've never ordered from www.servicehonda.com but, they are the cheapest at selling stock parts. You may have to call to order it.
I have ordered stock parts from www.bikebandit.com they usually costs a couple dollars more but they have excellent customer service, fast shipping and ordering is done online.
If you do order it through www.servicehonda.com let me know how it goes. I may start ordering from them. I'm checking the site now, it has an online order form.

[AbnMP13]

It's ordered, I'll let ya know on the shipping time.

[hornetgod13]

Good deal! I'm sure it will all work out for you. I may order from them in the future.

[zrpilot]

Originally posted by GPracer2500
I've ordered from SH many times. I think they have a $9.00 min shipping charge now so bear that in mind for small orders.

I'll keep ordering from then. They always have the lowest prices and shipping times are reasonable (usually a week). I place my orders online and that works well. I have called them too and was satisfied with the service.

Ditto!!:bandit:

I ordered a gasket and a RIGHT SIDE CASE for my '05 on December 29th and had the parts in my hands Jan 5th!! WOW!!!

[AbnMP13]

If it takes a week to get here then it'll get here same time as my exhaust. I got a 4 day weekend coming up and I'll try to ride Friday and Saturday, sposed to be crappy weather Sunday and Monday, if so I'll install the new jets and before next weekend I'll slap on the exhaust, throw in the needle and see how she runs.

[motown]

what notch is needle on stock:ermm:

[AbnMP13]

I BELIEVE in the 05 and 06 (I know the 06 doesn't) the needle doesn't have any adjustments. I don't know where the 04 and earlier is.

[Eviltanker]

I believe the 04 and earlier is on the 2nd. For what you are doing you might want to start on the 3rd. Thats where I started and actually went to the 2nd.
AbnMP13 You are right the 05 on to the 07 doesn't have the adjustment but, He's buying one from an earlier model.