jetting

[D-ACTIV8]

Is jetting something someone with basic knowledge of engines can do ? or would it be best to take it to a local dealer and have it done for me?

[nosliw]

you should be able to do it by yourself. easy-cheesy

[Mxracer53]

its easy im 13 and i jetted my 450r granted i will be 14 in a month
its real easy best an easiet way is to just change the main jet, what r u triyng to jet?

[D-ACTIV8]

im putting on a white brothers e-series header and pipe on a 2004 honda 400ex also putting a k&n air filter and an aluminum airbox on...this id my first attempt at doing any kind of mods on a four wheeler. any other tips from anyone would be most helpful

[nosliw]

jetting a 400ex is really easy. one thing you absolutely have to take your time on and make sure you do it right is taking those crappy goldish screws out. i stripped so many of those and it was such a pain in the *** to get out. i soon replaced them with stainless steel hex head bolts.

[hondardr4life]

Ya, its easy. I am 14 and have re-jetted my 300 3 or 4 times, The problem is getting the jetting right.

[D-ACTIV8]

I am still hesitant on trying to re-jet on my own...after reading other threads on this forum it seems rather difficult... anyone near columbus, ohio willing to do it for a few bucks??

[cals400ex]

send the carb to me and i will jet it for free. it is really easy. you just pay for shipping and the jets.

[CRE Performance]

Speaking of stripping screw heads out, I have a very useful tip I have been doing for many years and it is SURE FIRE!

Just before it gets stripped, or even after it strips, go to the local auto parts store and get some VALVE GRINDING COMPOUND, prefferably permatex brand. It should be similar to anti-sieze with sand mixed in it. Put a small wad on the tip of the screwdriver, then press down hard on the screw head and that baby will come right out;) This sometimes will work on bolts also.

The reason i passed this along is that im just now starting building quads and bikes and I notice there are a lot of overly tight and tend to strip even using my snap-on hand tools. I have built Ford race engines for years now and I have tore up enough **** and been in enough sitiuations, i have a fix for everything:D

[D-ACTIV8]

I mean...is it as simple as taking out one jet and putting a different one in? thats all?

[300exOH]

Originally posted by D-ACTIV8
I mean...is it as simple as taking out one jet and putting a different one in? thats all?

Basically yes. You may have to try a couple sizes to get it exactly right. I have done a couple quads now and I have had very little trouble. Here's a couple articles that should help.

http://www.exriders.com/techarticles/jetting.html

http://www.exriders.com/techarticles/sparkcolors.html

[300exOH]

Almost forgot...I would recommend using individual keihin jets instead of a jet kit. It's much cheaper and usually easier.

[cals400ex]

Originally posted by CRE Performance
Speaking of stripping screw heads out, I have a very useful tip I have been doing for many years and it is SURE FIRE!

Just before it gets stripped, or even after it strips, go to the local auto parts store and get some VALVE GRINDING COMPOUND, prefferably permatex brand. It should be similar to anti-sieze with sand mixed in it. Put a small wad on the tip of the screwdriver, then press down hard on the screw head and that baby will come right out;) This sometimes will work on bolts also.

The reason i passed this along is that im just now starting building quads and bikes and I notice there are a lot of overly tight and tend to strip even using my snap-on hand tools. I have built Ford race engines for years now and I have tore up enough **** and been in enough sitiuations, i have a fix for everything:D


just build chevy's and you won't have problems with crap breaking. :blah: :eek: :D

[AdvantageCycle]

Here's my 2 cents. Jetting is an art. First and foremost, you have to fully understand how a carb works, principals of pressure differentals, and so on. Yes anyone with a screwdriver can change jets, but thats not what I call tuning, not even close. You need to understand that all of the circuits in the carb over lap and not all to the same degree. Heres my suggestion to you. Change the main jet amongst trial and error, or have a professional do it. I use an EGA to confirm all of my jetting, you can do it by ear and reading the plug.

Oh, and the reply about the valve lapping compound.......Very true, but start with the basis of a good #2 phillips. Using those cheapies is a real good way to strip heads!

[CRE Performance]

Originally posted by cals400ex
just build chevy's and you won't have problems with crap breaking. :blah: :eek: :D

Maybe, but then id have to worry about getting outran:D

[400ex men]

im 15 and i RE jet bikes all the time:)

[JRP]

its realy esy the problem is just tring to find out the perfect jetting. (i still cant find it out):ermm:

[Bush0102]

how will i know if my jet is perfect?:confused:

[cals400ex]

Originally posted by Bush0102
how will i know if my jet is perfect?:confused:


what everyone calls perfect is very different. i have seen dynos even vary greatly. one individual will want a keihin 150 on a piped and filtered 400ex and others will want a 180 on the same bike. that is a large difference. i can promise you the top end power with the 180 in will suck, given you live in moderate temperatures and elevation levels. on this bike where i live (625 feet above sea level), i would run somewhere between a 152 and a 158 depending on air box modifications and the temperature outside. a bike jetted too big may just run fine, but it will be no where near its potential. when the bike is jetted lean, i notice that midrange power seems alittle less. when rich, the mid-top end power will more or less bog.

[CRE Performance]

Any of you guys ever tried or thought about welding in a o2 bung in the exhaust pipe, sticking in a cheap o2 sensor for tuning then removing and capping it off?

[cals400ex]

Originally posted by CRE Performance
Any of you guys ever tried or thought about welding in a o2 bung in the exhaust pipe, sticking in a cheap o2 sensor for tuning then removing and capping it off?


yeah, i have thought of that but i didn't want that plug in my exhaust.