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Discussion Starter · #1 ·
i just bought an HMF slip on for my 2004 400ex. if anyone else has a 400ex with this pipe could you please guve me a review on it? thanks
 

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oh ya and i ordered it online so i didnt get it yet and im getting antsy and want to know if someone with my same quad likes this pipe
 

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I have the comp series, HMF makes an absolutely amazing product. I had a 2 bros. system before that. HMF is light years beyond 2 Bros.
 

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i just bought an HMF slip on for my 2004 400ex. if anyone else has a 400ex with this pipe could you please guve me a review on it? thanks
LOL...I was gonna say it's a little late for a review since you already ordered it...then I saw your next post. This will be my next mod...let me know how it goes.
 

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Great pipe to have. I love mine. It wakes up your machine like a mad man but you need to do the supporting mods. Jetting the main and pilot jets to a 165-170 main and a 42 pilot, remove the air lid, better filter(K&N) or a (UNI) and filter cover, and a aftermarket cdi box. You also need to move the needle clip one notch down from the factory setting. If your needle dosent have the knotches, you will need to get the older adjustable style. Best of luck,
Nick
 

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Discussion Starter · #6 ·
thanks everyone.
Redracer: do you have just the slip on?
Green: ok i will. i should be getting it hopefully by atleast thursday
njrextreme: Whats a needle clip and where is it?
 

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Whats a needle clip and where is it?
The needle clip clips onto the top of the jet needle and the jet needle is located in the throttle valve, which is in the center of the carb. You have to take the top of the carb off to get to it. The jet needle has notches on the top that the clip snaps on. To lower the needle, raise the clip. To raise the needle, lower the clip. The newer 400EX carb doesn't have an adjustable jet needle, but the older carbs do. Below is a picture.

 

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I have the slip on.


 

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ok thanks. what changes when you move the needle?
More fuel air mix. You dont have to move it. Im just telling you how to get the most out of the slip on pipe. I would look into buying a aftermarket jet kit and download the service manual.
 

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You can download the service manual at the link below.

maxmekker.com
 

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what is the difference between the comp vrs. the sport add on. i am sure it's the price for starters, but does it depend on the machine match up or can you use either?
 

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The comp series is more agressive
 

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About the HMF Competition Series:The new HMF Competition Series exhaust was designed and tested for Sport ATVs and Dirtbikes. The Trimax Core technology features 3 levels of power and sound, allowing you to dictate the type of power and sound you need, when you need it. Included with every exhaust are 3 removable inserts, each of which effect the sound and power in different ways, giving the rider complete control.
Stage 1 uses an insert that restricts sound levels extensively yet produces industry leading power at that dB level.
Stage 2 uses a different sound altering insert that partially lowers sound levels without losing much horse power.
Stage 3 acts as an unrestricted core producing high dB levels with industry leading power throughout the RPM range.
The new Euro End Cap is forged out of 304 Stainless Steel and adds an incredible sound output. Stainless Steel rivet bands are wrapped around the shell and air riveted in for more durability and security.

About the HMF Performance Series:Setting the standard for power and value, the HMF Performance Series has been tested for over a decade with endless championships. The specially designed, unrestricted core allows the exhaust to increase power evenly throughout the entire power curve. The Performance Series has the signature HMF sound with industry-leading end cap and color options, giving you a completely custom look and sound.

Specifications for 400EX (99-10)
Horse Power Increase
HMF Slip On System

3000 RPM: +4 HP
4000 RPM: +4 HP
5000 RPM: +2 HP

HMF Full System
3000 RPM: +4 HP
4000 RPM: +6 HP
6000 RPM: +3.5 HP
7000 RPM: +4 HP

Torque Increase
HMF Slip On System

3000 RPM: +8 ft/lb
4000 RPM: +9 ft/lb
5000 RPM: +9 ft/lb

HMF Full System
3000 RPM: +8 ft/lb
4000 RPM: +9 ft/lb
5000 RPM: +9 ft/lb
6000 RPM: +4 ft/lb
7000 RPM: +4 ft/lb

Jetting
1999-2009: Slip on: 165/170 Keihin Hex
1999-2009: Full System: 180/200 Keihin Hex
 

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It will make you a tad lean, nothing dangerous. Especially considering you are already at sea level. It will change tone but not much more.
 

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Discussion Starter · #20 ·
ok thanks. what changes when you move the needle?
More fuel air mix. You dont have to move it. Im just telling you how to get the most out of the slip on pipe. I would look into buying a aftermarket jet kit and download the service manual.
ok. i just put it on and it sounds great. do i have to rejet it?
 
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