[Aqualungs]

Got an awesome price on Ebay brand new for my 08 400ex. Been feeling like I need a little more oomph sometimes.

HMF Full Red Exhaust Pipe Honda TRX400 TRX 400 400EX: eBay Motors (item 200514183243 end time Oct-17-10 08:36:56 PDT)

Also ordered EHS custom airbox lid

EHS Racing 400EX Custom Airbox Cover Air Box Lid

and a Uni filter.

I think i will get that extra power now.. :lifting: :icon_ banana:

 

[Redracer]

You will love the power gains, make sure you either rejet or have someone rejet your quad. If you don't you will be running extremely lean

 

[DAN400ex]

I did something similar with my 400, love the power gains and sound, and you'll experience more gain due to the full exhaust kit.

 

[Aqualungs]

Yea they're sending me a jet kit. Have some experienced help.. to help me. This is my first quad. I've had it 6 months, and it feels like an extension of me. I can't wait to hear this sucker purr. Just need a little more punch. I do a mix of trails and some messin. Time to let this baby breathe!

Dan, i almost did a slip-on, but $410 for a full exhaust and jets.. well I had to! I really only needed the power of the slip on, but then again 6 months ago I thought this thing was way too powerful for me, and now I want a little more. So I'll be taking it easy once the mods go on, i'm sure there'll be quite a difference.

 

[Aqualungs]

BTW nice quad!

 

[DAN400ex]

Thanks. Let me know who you like that HMF exhaust system, it was a little expensive for me to put on a 400. When I get a 450r someday I'll definitely put the full HMF exhaust on it, that would be well worth it. But for the time being I really do love my 400. I mainly use it to trail ride and take it to my buddies mx track every other weekend or so.

 

[Aqualungs]

I have a question for the HMF exhaust they sent me two jets. 180 KH and 200 KH. Do I need a pilot, too. This is my first time doing this, so I want to make sure I do everything right. This is what HMF recommended, but they said nothing about the pilot. I will be running and EHS lid (open lid Outlaw filter) with a UNI air filter.

 

[Redracer]

You will know instantly if you need something other than the main jets

 

[DAN400ex]

I have a question for the HMF exhaust they sent me two jets. 180 KH and 200 KH. Do I need a pilot, too. This is my first time doing this, so I want to make sure I do everything right. This is what HMF recommended, but they said nothing about the pilot. I will be running and EHS lid (open lid Outlaw filter) with a UNI air filter.

When I upgraded my 400 I went with a 42 pilot jet. I would guess you should place a 42 or even go up to a 45 if not higher due to your extra air flow. When I upgraded I make the mistake of putting my atv all back together before test driving it and had to pull it all apart a week later cause I forgot to put the plastic ring that goes around the main jet back in. I would make sure it runs smoothly before you replace all your plastics. Otherwise you will be pulling everything back off and its a pain! Check you spark plug to to see if you running to lean or rich before you replace everything too. Here is a page you can use to help you with spark plug reading.

Spark Plug Colors Reading Instructions - ATV Technical Articles

 

[Aqualungs]

So what is a 180 and a 200? Do i need both of these and a 42 pilot. Or is one of these supposed to be replaced by the 42 pilot.

 

[jkhuntin]

Those are both main jets, to let you fine tune for elevation and air flow. You definately don't want to replace your slow jet with one of those, I don't believe that she would run very well.

 

[DAN400ex]

So what is a 180 and a 200? Do i need both of these and a 42 pilot. Or is one of these supposed to be replaced by the 42 pilot.

Like jkhuntin said, the 180 and 200 are main jets and you can only use one at a time and only on the main jet, you will have to determine which one is appropriate by trial and error. When you pop the bottom of the carburetor off the main jet will be sticking up and have a plastic baffle around it (don't forget to place the baffle back where it was). You will want to remove the stock 148 main jet (6mm socket) and replace it the 180 or 200. I'm not sure which one you will have to go with but I would personally start with the 180. (I have a 170 main jet because I don't have a full exhaust kit on, just a slip on) Now if you do decide to replace the pilot jet its going to be next to the main jet but sunk down in the carb and you will need to get a flat head screw driver to get it out. Hear are the instruction for doing so...

Honda 400EX ATV Pilot Jet Insturctions - ATV Technical Articles

Like I said earlier I would leave all of your plastics off and make sure your atv runs right before you put everything back together. It will make it a lot easier to fine tune. If you want to talk to me via phone for more questions let me know, just send me a private message and I can give you a call.

He is some additional reading that will help you understand carburetors a little more as well.

ATV Carburetor Jetting Instruction - ATV Technical Articles

Once you get all of this done, if you atv pops or back firers when driving you are running to lean and will have to get a larger jet, if its not really running or sputtering and losing power you are running to rich and will have to go to a smaller jet. Its all trial and error so fine tune your 400 before replacing the plastics! It will save you a lot of grief! Let me know if you need anymore help.

 

[Aqualungs]

I sent an email to HMF, this is what they sent me

"Marty, 05 and up models have a different carb. Start with a 152 main, and a 42 pilot jet. You will also want to adjust the fuel screw to the highest smooth idle with the engine warm. Then you can set your idle using the idle adjustment knob."

This is what someone posted on another forum.


"A 400 is a great ride, arguably the best trail bike made. You are headed in the right direction....with the mods you mention you will only need to change out the main jet, I would try the 180 first to see how it runs.

Do us all a favor (and for the sport of atving too) and get a quiet core insert if you are going to be riding on any public lands or near neighbors....the HMF is a bit loud without the quiet core and we want to keep everyone happy, because land closures happen when everyone is not happy"

Looks like trial and error time!

 

[Aqualungs]

BTW thanks Dan for all your help!

 

[DAN400ex]

No problem, hit me up anytime!

 

[Aqualungs]

I sent an email to HMF, this is what they sent me

"Marty, 05 and up models have a different carb. Start with a 152 main, and a 42 pilot jet. You will also want to adjust the fuel screw to the highest smooth idle with the engine warm. Then you can set your idle using the idle adjustment knob."

This is what someone posted on another forum.


"A 400 is a great ride, arguably the best trail bike made. You are headed in the right direction....with the mods you mention you will only need to change out the main jet, I would try the 180 first to see how it runs.

Do us all a favor (and for the sport of atving too) and get a quiet core insert if you are going to be riding on any public lands or near neighbors....the HMF is a bit loud without the quiet core and we want to keep everyone happy, because land closures happen when everyone is not happy"

Looks like trial and error time!

I should go with HMF's reccomendations, right?

 

[DAN400ex]

It looks like you have two replies from two different people, what did they tell you to do? Also remember you have to compensate for your EHS powerlid, not just the exhaust system. But tell me exactly what HMF told you to do.

 

[DAN400ex]

Also on a second note I'm pulling apart my 400 again this weekend and I'll take pictures to help you out if you can stand to wait I can post them for you on saturday evening so you can get a visual.

 

[Aqualungs]

I told him exactly what I had UNI filter, EHS lid, and HMF full exhaust. He said 42 Pilot and start with 152 main and go from there

 

[DAN400ex]

That makes me nervous because I have less air flow than you and he wants you to start of with a smaller jet than I have (170) which would make you run very lean and if you do that there is the chance you can seize up you engine... I hate to say this but I think he's wrong in this case. Tell you what, go to my page and on my friends box, (I only have 3) click on TRX2five0. Ask him to take a look at your link. He's the one that advised me when I was asking my questions and he steared me correctly. He really knows what he's talking about. I'll try and direct him to this link as well.