ANOTHER Jetting ????

[400EXIAN]

I have heard ppl talk abou tjetting without buying the kit??? Just buying single main jets does this work if so why doesnt everyone do it if not why not??? I would like more info on this as mine allegedly has a jet kit but when igot it it had the factory pipe "Gutted" and now i put that big gun on and it backfires quite a bit....So i am going to re jet just wondering the best route to take

[Fuchs42]

go to your local shop and buy one single jet for 3 dollars if your running stock 148 buy a 150 or 152 main and it should run better. just my $00.02

[250EXking]

i just got the kit. i have changed jets quite a bit to find the ones i like. just my opinion.

[JOEX]

The jet kit that every one seems to talk about is the K&N/DynoJet kit. I personally do not have any direct experience with it.

The only advantage I see is the tapered needle.You can adjust the stock needle if you want.

The individual main and pilot jets run about 3-4 dollars a piece. From what I hear a 152 or 155 main will work with most aftermarket slip ons.

A pilot jet increase will probably a good investment.... a 40 or 42 should be be fine but you might want a 45 if you remove the choke.

Joe

[400EXIAN]

Ok fellas dug into the carb and sure enough it has an aftermarket Jet kit (b/c of the tapered needle valve) However the main jet is a 146!!!!!!!!!!!!!! Seems a little lean to me the plug is WHITE!!! what jet would you guys recomend and how should i get one since i already have a kit i dont want to shell out 50 bucks for another kit!!!

[H440exconfused]

I dont know what kind of a jet kit it has, the stock needle is tapered too, and that jet size is stock, 146= stock.

I am with Fuchs42 i think a 150 or 152 will be what you are looking for with the airbox lid on. Needle on 3rd position. I would start with the 152 first then go down if you are not happy. Get yourself a couple plugs with those jets too and run a new plug with each jet.


On the backfiring, it sounds lean to me especially if it pops and backfires on deceleration.

[400EXIAN]

I was under the impression stock was 148>>> That is what dirtwheelsmag.com says and so does everyone else on here!?! Isnt the stock needle rod a brown like color as where the after market needle rods are silver also when i was looking at the bolts that hold the bowl of the carb on you can tell someone has been in there before me...

One more question Pilot Jet: should i go 42 or 45 with no choke?!?

[sparks400]

i read under dynojet that if u have a open airbox, below 3000feet, aftermarket pipe and k&n u should run a 170 main, is that right?

[cals400ex]

the stock mainjet for a 400ex is a keihin 148. my friend has a big gun slip on and k&N filter and we are at a little above sea level. in the summer months, a 152 keihin is right on. in the winter, a 155 is used. that should get you really close.

[400EXIAN]

So why would mine have a aftermarket 146 in it??

[Doibugu2]

cus they didn't know what they were doing.

[cals400ex]

yeah, i would bet they either don't know what their doing or that they thought the stock mainjet was something smaller than a 148.

[400EXIAN]

So i bought a 42 and 45 pilot jet which should i run i have already removed the choke

[cals400ex]

i would try the 42 first.

[JOEX]

Originally posted by H440exconfused
I dont know what kind of a jet kit it has, the stock needle is tapered too, and that jet size is stock, 146= stock.....
From what I understand the Dynojet needle has a different taper than the stock needle which could be more advantages.
Stock 400ex main is 148 ...... or 142 for upper elevations.

A 42 pilot could work depending on you area, weather/elevation etc... but with the choke removed you might need the 45. Just try them out and see what works for your situation.

Joe

[400EXIAN]

Ok so now i got the rest of my buddy's jets the freaking DYNO JET jet kit calls for a 10 main jet if running after market exhaust and no airbox lid!!! That is what my buddy put in i looked at my big gun literature today and it calls for a 155 however i just cut 5" off my big gun and now run w/no airbox lid so i figured i would try a 160 first i just got to ride it about 15 min. power was good... way better than stock i checked the plug but dont think i rode long enough to tell anything what do you guys think you think it is too rich??i can smell the fumes more now than before (of course before i was running a 146 Main jet???!?!) So anyhow what do you guys think?

Also with these mods woould i notice any difference if i bought one of those CDI boxes? (ie Big gun, white brothers.........) My buddy who put the 170 main in with the same mods as me bought one and put it in the same time as the jet kit and swears he notices a huge difference on top end??? How could he tell if he just did a jet kit too? Anyhow any info is very much appreciated!!
Thanks
-Ian

[cals400ex]

i think you have a misprint. a 10 mainjet??? a 155 dynojet mainjet will probally give you a little more power if all you have is the pipe a no air box lid. smelling fumes may also be a sign of being rich. well i just ordered a cdi box. i think my friend gained a little top end out of his. i ordered the curtis sparks box just because i have a few of his other product and love them. he is also one of the best engine builders. i don't know if there is any difference between the aftermarket revboxes or not. my second choice would be the big gun box. most people say these boxes are a waste until you have engine mods but i know my friend gained a little top speed out of his. you will not get a seat of the pants difference though.

Is it possible to buy just the dynojet needle from anyplace???

[hondafox440]

Jetting isn't an exact science. Temperature, compression, mods, altitude, and humidity all affect it. If your plug is white, your main is too lean. Go to your Honda shop and buy a main 1 size bigger, and a main 2 sizes bigger. Throw the 1 size bigger in and do a throttle chop test, then check the plug. If it's still lean, go for the 2 sizes larger. Ideally, a correct main jet will yeild a mocha-tan colored insulator after a throttle chop test on a new plug.

As for the pilot, warm the machine up, and ride it from 1/16th-1/4th throttle.. If it surges and just sounds rough and sputtery, go up a size or 2. The pilot should be adjusted before the main.

[400EXIAN]

Ok guys i started with a 160 w/ 5" chopped off the big gun and no airbox lid (good power) went down to a 152 in fear of being to rich (lost power) went to a 155 (gained some back but not like the 160) so back to 160 (feeling good again) so for SH!+s and giggles i went on up to a 165 (wow!! better power than the 160 even) no lowend bogging or spddering or anything just solid running machine! However i took my plug out today after a few days of hard riding on trails and a lot of wheelies and the plug is pretty black?!?! should i go back down a jet? I dont really want to i do like this power! However by the plug it appears to be running rich? Are there any dangers in running a little rich? Could i just be imagining this extra power with the 165?? I know it comes up WAY easier in 3rd and 4th with the 165 than any other jet! Also i am running a 45 pilot and no choke! Should i quit worryin' and RIDE or should i do more jet swapping and take a loss in seat of the pants performance????
thanks
-Ian

[cals400ex]

i personally say the 160 will give you more power. i would race another 400ex with both the 160 and 165 in. the additives in the gas anymore make it hard to look at the plug for readings. i am running a sparks x-6, no lid, uni filter, no choke and with a 165 in, i was actually slower than before i got my pipe. after rejetting and rejetting, i find mine is fastest with the 160 in. i just keep racing my friend on his 400ex until i found the best mainjet. i already have a 150, 152, 155, 158, 160, 162, and 165 mainjets so i can fine tune as the weather changes.