Choke removal and header mod!!! WOW

[416racer]

I did these mods this weekend and got to try it today,Man was I impressed! It wasn't like a ton more power but enough to beat the guys I ride/race with. One guy has a piped and jetted z400 that used to beat my by a few quad lengths untill I did my 416 with 11-1 and stage one HC
then we were about even,now with these mods I was pulling him by 3 lengths. The other guy has a piped and jetted ex but he is 100lbs. lighter than me,I figured he'd still get me but damn I got him too! defintly worth the time and sanding pads for my dremel.:D

[a4guy]

Got my exhaust off right now since the quad is under going a major face lift. So I am going to grind these down tomorrow.

[416racer]

I painted mine with the silver BBQ paint while it was off. the header washed off pretty good even after 5 hours of baking the mud on it

[hocman123]

when u grind the header welds dwon do u need to rejet b/c i suck at honda carbs and it would suck to pay someone to do it

[416racer]

I'm pretty sure that I read on here that you do. I'm not for sure. I was running a little rich before I did these mods and now it's seems right on.

[hocman123]

umm maybe i will do it when i get a new pipe that way i only pay once

[a4guy]

So the head pipe is sitting in the vice, I grabbed my dremal box, opened it and all my bits are gone. Lent it to a friend and got it back with no bits. So I guess I will not be doing it till tomorrow.

Anyone know what jetting changes need to be done if any after this is done?

[ish416]

I have done these mods way back when I was still running the stock headpipe and carb. For me, there was a slight difference, maybe a single HP but nothing that would equal 3 quad lengths in a drag.

At least that was my experience.

I was also running a 416 12.5:1 with an XR cam, FMF Powercore 4 slip on, kn filter and open airbox at the time I did this mod.

For those that are interested in the choke removal mod,HERE (http://www.atvriders.com/articles/choke400ex.html) is the link.

[slightlybent47]

Sorry to break it to you but by just doing the header welds and taking choke off is not going to make much of a deference. If you are running a stock ex then just change the main jet from I think the stock jet is 142 so go up to a 147 witch is the next size up and you’ll be fine.
The main jet is easy to change, just take a 17mm end wrench and reach up under the carb and remove the plug from the bottom of the bole. First turn the gas off.

Then take a small ¼” end wrench and remove the main jet sticking down past where the plug came from.
Replace it with the right one and your set to go. Just make sure you don’t over tighten the jet. It’s easy to strip if you don’t get it started right.
You should be able to change it in about 5 minuets.

your talking about a very small gain with this mod, most of what you are seeing is just a better throttle responce and not more power.

With so many things that affect performance such as traction, and riding skill it would not surprise me if anyone can feel the deference, with this mod.
It would take a highly skilled rider to tell if the mod had been made.

[a4guy]

Not saying I'm going to gain major hp results with this but if I can do something to better my quad then I'm going to do it. I do not race or anything like that. I am a trail/woods rider. I like to get what I can out of my machine. Thanks for all the help.

[slightlybent47]

Don’t get me wrong, any mod that helps in any way is welcome, especially when you only have 28 hp to start out with, even a one hp gain is better then nothing. And if your willing to do the work, every little bit helps and there is nothing wrong with getting the best out of what you have. So go for it. It’s an easy mod.

[eotrx400ex]

after i did the choke mod and a 42 pilot i felt a difference. off ideal was little more torque.