______Carburators: I don't understand them!_______

[Brauap]

I just know the basics. But I want to know:

What is the stock jetting?
Say if there is this scenario:
I have an air filter that needs the jetting at 159
I have an exhaust that needs the jetting 191
I have a header that needs the jetting 162
(these where all just made up ;) )

What jetting would I use?
How do you determine that?
Is it hard to jet?
How do you start to guess what jetting needs to be used?
How do you know if you need to adjust the poilet or the other jet.
What is the other jet's name?:p
what is the fuel screw?
what does it do, how do you adjust it?
where is it and how many turns should i have it at?
if im not sure what its at right now, would you reccomend checking it?

My final questions are:
Could you please post pictures to help me understand?
I have heard that JetsRUs is a good site, but is it?
I have a K&N what should I jet it too? The man at the local Honda Shop said to go up 2 jets. What do you think?




Thank you soo much!
-------Braaup (Colton)
:):D:cool::devious::chinese::p;):o:ermm::uhoh:

[jesseweaver]

dude chill with the smileys:D

i dont really know a lot about that stuff, but id say your best bet would be to get a jet kit and try a bunch of different jets and see where it runs the best. oh yea the "other jet" is the main jet. its not really hard to jet it, just kind of time consuming. you gotta take plastics tank and everything off then take the carb off then screw the jets out. heres an article from this site on how to change pilot jets. http://www.atvriders.com/articles/pilotjet.html

[jesseweaver]

oh yea, for people to tell you the right jetting, your gonna need more than "I have a K&N" you also gotta look at the rest of the mods and elevation and weather (temps.) and stuff.

[Brauap]

Originally posted by jesseweaver
dude chill with the smileys

i dont really know a lot about that stuff, but id say your best bet would be to get a jet kit and try a bunch of different jets and see where it runs the best. oh yea the "other jet" is the main jet. its not really hard to jet it, just kind of time consuming. you gotta take plastics tank and everything off then take the carb off then screw the jets out. heres an article from this site on how to change pilot jets. http://www.atvriders.com/articles/pilotjet.html
------
oh yea, for people to tell you the right jetting, your gonna need more than "I have a K&N" you also gotta look at the rest of the mods and elevation and weather (temps.) and stuff.


Can't you tell I am bored? lol

I live in ohio. Probally, Roughly the save elevation as you, if you not in the PA mountains. It verys from 7 to 45 now. about 50 to 90 durning the summer. Could I put a 42 poilet in to make it easier to start in the winter but leave it in durning the summer? I have no other mods that needs to be rejet. What jet would you recemend? or dont you know? Also, one more question, what is the difference between the poilet and the main jets? like what different jobs do they have?

Thanks sooo much!

[jesseweaver]

you should be good with a 42 pilot in during the summer. as long as your not riding really hard in like 100 degrees. id check your pilot first though. i paid like 15$(mostly shipping) for my pilot, and when i put it in i saw it already had a #42 pilot jet in. im not sure with the jetting for you either. come to think of it i dont even know what main i have in mine. i think 175, would this sound right with my mods?

also, not trying to jack your thread, but what is the fuel screw? what does it do, how do you adjust it (where is it), and how many turns should i have it at? if im not sure what its at right now, would you reccomend checking it?

[Brauap]

No problem! Your aloud to ask questions too! I'll ad them up top. Hey, could you get on AIM so we can talk like that?

[Brauap]

Can anyone else help me please?

go to www.jetsrus.com and read their faq on jets and jetting and also reading a plug...

there is an article in the "Artticles" secion of this site on reading plugs has pictres and descriptions of why the plug looks like what it does. Very helpful

[F-16Guy]

Reading a plug, in my opinion, is pretty subjective and readings can vary depending on the kind of fuel used and the conditions at the time the plug chop was done. I really think it's better to do it by feel. Start with a jet that you are sure will be too rich and start working toward the lean side. When you get to a leaner main jet that showed no improvement in wide-open-throttle (WOT) performance or is worse than the previous one, go back to the next richer jet. At that point the main jet is good and you can work out any partial throttle stumbles with the needle. Any hard starting or off-idle issues can be fixed by adjusting the fuel screw, or by changing the pilot jet if the fuel screw won't give enough adjustment to solve the problem. I think you should start with the main jet first, then the needle, and finally the pilot jet.

I will be jetting my 400ex to my HMF and K&N sometime within 2 weeks. Now do you have to ride the quad to tell if the jetting is right or can I either put it in neutral and see if it stumbles going to WOT and back to idle or should I set the back wheels off the ground and run it through gears? Where I live I deffinately cant rde it around my house with an HMF.

[boosted3g]

You have to have a load on the engine. Better to do it in a higher gear also so it takes longer to rev out.

[Hondamaster5505]

Seems no one answered this question yet, although if you did, sorry!

The difference between a main jet and pilot

Pilot- controls fuel from idle to 3/4 throttle.

Main- Controls fuel from 3/4 to WOT


I dont know much else about carbs other than that, all i know is that i have to jet it and ride :D

If its anything technical i just have my dad help me so i could learn all this stuff.

I could most likely rebuil an engine and everything, just by watching my dad work on this stuff and helping out a little bit:)

Originally posted by Hondamaster5505

Pilot- controls fuel from idle to 3/4 throttle.

Main- Controls fuel from 3/4 to WOT


[/B]

wrong...the pilot only controls to about 25-30 throttle...the needle controls from about 20-25% until about75-80%, then the main handles 70-75% on up to wide open throttle

airfilters, headers, and exhausts all factor in what main jet and needle setting you need. they don't have their own set jetting need. think of it this way, the more air you flow, the more fuel you need, meaning a larger jet. if you add more air flow, go bigger, if you take some flow away, go smaller.

it is always better to run a little rich(more fuel), than lean(less fuel). the fuel will actually help cool the cylinder some, running lean will make it run hot. Too hot and you can burn things up.

and yes, you need to be riding the machine at wide open throttle to take a plug reading. plug reading is not as subjective as feel of the pants...most of these guys wouldn't notice the difference between a 170 and a 165 jet in their machine if you told them what to "feel" for. if i had my choice, i would do a dyno run every time...

oh and stay away from jet kits

[Brauap]

Originally posted by Hondamaster5505
If its anything technical i just have my dad help me



My dad won't help me, he's kind of.. chicken with the jetting and motor work.. I would do it all, but ooh god, he dosn't like when I say that!:ermm:

Originally posted by boosted3g
You have to have a load on the engine. Better to do it in a higher gear also so it takes longer to rev out.

man i have no clue how i'm going ot get my quad jetted right. I have nowhere to ride it close to home. Only 25 minutes away which i cant chnage the jets out there cause theres so much dust always in the air you carb would be clogged by the time your done.

[Brauap]

[B]I have 2 more questions!!!! I need these answered A S A P !!!


1) What is the stock jetting!?

2) What should I do? Buy a JetKit or but seprate jets from JetsRUs? Also, I was thinking about a dynojet kit, but I saw on another thread, that the nubers on there are different than they really are.. I am just strating to understand these numbers...

[Brauap]

Oops! One more! Should I buy the jet kit off of JetsRUs? Here is what their site says..

" Honda TRX400EX & 400EX jet kit $29.98


The jet kit comes with all the following brand new parts: Main jets: 152, 155, 158, 160, 162, 165, 170, 175, 180 and 4 stainless steel allen head bolts for the carb bowl. Instructions on jetting included.

This kit is for modifications such as the following: aftermarket air filter, air box lid removed, modified air box, aftermarket slip-on exhaust or completely modified exhaust or cams."

I am not going to do anything more than an exhaust.. would you guys recemand it? Please answer these first.. I need to rejets asap so I can go riding! Please HELP!!!!!

[Brauap]

I just found the stock jetting.. so I dont need that answer...

[Hondamaster5505]

Originally posted by Brauap
My dad won't help me, he's kind of.. chicken with the jetting and motor work.. I would do it all, but ooh god, he dosn't like when I say that!:ermm:

My dad is weary of touching someones elses bike if it needs a rebuild or something. He feels if he does mess up he would rather be on his own bike then a customers bike.

He does machine work, like grinding etc. But he does atv/motorcycle/lawn tractor+mower/snow-blower repair on the side.

Originally posted by Brauap
Oops! One more! Should I buy the jet kit off of JetsRUs? Here is what their site says..

" Honda TRX400EX & 400EX jet kit $29.98


The jet kit comes with all the following brand new parts: Main jets: 152, 155, 158, 160, 162, 165, 170, 175, 180 and 4 stainless steel allen head bolts for the carb bowl. Instructions on jetting included.

This kit is for modifications such as the following: aftermarket air filter, air box lid removed, modified air box, aftermarket slip-on exhaust or completely modified exhaust or cams."

I am not going to do anything more than an exhaust.. would you guys recemand it? Please answer these first.. I need to rejets asap so I can go riding! Please HELP!!!!!

i'm doing the same thing, i dont need that kit because I just bought 6 steel screws from Lowes to go in my carb where the crappy screws get stripped. I need to buy jets real quick and i'm going ot go with JetsRUs but I think I can do without a 175 and 180 main.

[F-16Guy]

The JetsRUs kit is much more practical and reasonably priced than the Dyno Jet kit. You can buy jets individually if you know what you need (or close to it), but if you want to experiment, the JetsRUs kit looks pretty good. The Allen head float bowl screws are a great idea, too. Realistically, with no internal mods like a piston or cam, you shouldn't need over a 155. If money is an issue, just buy 150 through 155 main jets and a 40 pilot jet. If you have a little extra cash and think you might do a piston and cam later, get the kit.

it is worth the extra cash for the jets because later if you need them now you have to spend $7 shipping on a few more jets. If you buy them all at once you will have every jet you need for the future unless you get a big bore and such.

[maclavin]

man i have no clue how i'm going ot get my quad jetted right. I have nowhere to ride it close to home. Only 25 minutes away which i cant chnage the jets out there cause theres so much dust always in the air you carb would be clogged by the time your done

You can do it at Croom. You don't need to take the carb bowl off and you dont need to take the carb off the bike to change the main or the pilot. Just take the plug out of the bowl and loosen the carb a little bit to turn the carb for better access to the jets.

[JOEX]

Originally posted by FoxHondaRider
it is worth the extra cash for the jets because later if you need them now you have to spend $7 shipping on a few more jets. If you buy them all at once you will have every jet you need for the future unless you get a big bore and such.
In you case I doubt you'll never need a main over 160, probably 155.

I bet C&D Racing will have a better cost including shipping.

[TheNewn]

In my opinion, you're making it way more complicated than it needs to be...

Your mods are full exhaust/air filter? Just go up 2 sizes on the main, a richer setting on the needle (move the clip down) and the fuel screw 2.5 turns out. It should be in the ball park, ridable by all means. And you can fine tune it once you've gone out to ride and figure out what its doing/needs.

Buy a Clymer manual for one if you don't have it, you can see a blow up of the carb and what everything is labeled as.

There are many places on the internet and here (use the search feature...) that will help you with everything.

[jesseweaver]

would a 175 main and 42 pilot sound right with my mods? i just checked and thats whats in.

[TheNewn]

...Well...how does it run? If it runs well, and you don't know what you're doing, don't mess with it.

[F-16Guy]

A 175 sounds pretty rich for a 416 unless it has a really high compression piston, oversized valves, and some port work. I would buy the next three sizes smaller and start going down one at a time to see if the power improves. If the full throttle power keeps getting better, keep going down to the next main jet until you see no improvement or it gets worse, then go back up one. A 42 pilot is probably fine with the mods you have.

[jesseweaver]

is there any way to tell the compression of the piston? all i know is its a Wiseco and the guy i got it from just said its high compression. im running pump gas through it so i hope its not like 12:1 or something. and i dont think there is any porting done, anyway i can figure that out?

[F-16Guy]

It's probably an 11:1 piston, which you can most likely get by running premium pump gas with. If it were a 12:1 or higher piston, you would here a knocking or pinging sound under hard acceleration unless you ran race fuel. If you wanted to know for sure, you could have a shop "cc" the combustion chamber and figure the exact compression ratio, but it's not really necessary unless it's knocking or pinging. If it is, don't ride it without race fuel because you will severely damage the engine very quickly. As far as jetting goes, I would try a 165 main jet, needle clip in the third groove from the top, and a 40 pilot jet with the fuel screw about 3 turns out from lightly seated.