400EX Headpipe to ATC 350X with 450R Silencer

[MN250R]

Well, I finally tackled the 400ex headpipe on the ATC 350x task. I looked all over the internet to try and get info about doing it. Here is what I came up with.
The 400EX headpipe fits the the head, I did however have to drill the flange holes open a little larger to fit over the exhaust head studs. I also hacked off right after the part on the exhaust where the pipes come together. I tried to take measurement. See Pics.
I did also have to buy some pieces from Orielys to make it work. See Pics. I admit, to make it look right you will be fiddling around for a while, grinding, using flapdisk, vise, welder, even the heavy duty flaring tool i bought. Here are some pics. I will update throughout the next few days as i took ALOT of pics :)
Here is the pipe compared to the stocker. Dirty picture is of the 400ex headpipe as i got it and after sandblasting it.

[MN250R]

Here are some pics of measurements i took of inside diameter. 400ex headpipe is the cleaner of the two since i sandblasted inside of it in my cabinet :) Also i got a reading of 27mm vs 23 mm stock. Maybe from the weld on the inside of the flanges or not. Not quite sure. 400ex pipe did look larger to the eye at least to me.

[atc007]

I have a 400EX headpipe I bought from a member here. It has the first cut done to it. That's it. I think I paid him $70 shipped. I would sell it for what I have in it if anyone needs it. Nice work Mn !!

[salisbury4573]

I already have a 400ex head pipe and want to do this mod as well, please continue to post up your pics as they are very useful and will hopefully help guide me on my cutting and welding.

Thanks for posting this.

[MN250R]

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[MN250R]

Here are some more pics on the 400ex head pipe on atc 350x. I found out that the 400EX head pipe does fit the head. The holes needed to be drilled a little bit bigger on the 400ex flange as the studs on the ATC 350X did not quite fit. Just a hair bigger than 3/8. I took some pictures of the pieces that I used to make this conversion. I also ended up using a silicone high temp coupler where the exhaust meets at the back. As I was unable to make the system be almost a complete hook up to the back due to the frame getting in the way. I also use the black heavy duty pipe spreader as you can see in the picture to flange the pipes to fit. Once in place a tack welded pieces in. After it was fitted in I took it out and mig welded it. Then I used 120 grit flap disc to grind the welds down that would be seen on the back side of the pipe. The front weld that connects the new pipes to the where the pipes come together was covered by the heat shield so i left them as you can see in the picture. I then used pj1 high temp 1500 black paint on the header . I think it turned out okay I'm not a welder by trade it's kind of a hobby for me and I believe it looks better than the factory head pipe that I had see pictures. I also will be wrapping the exhaust with black exhaust wrap, with the hightemp black silicone spray. Finally, i will high temp paint the exhaust shield white.
Also here are the links to the High Temp silicone HPS connector i bought off Amazon and the stainless muffler clamps/ pipe flaring tool. ( You could get by with some other flaring tool i guess but i would use it for more than just doing this exhaust so thats why i bought it :)The other exhaust parts were from Orielys. Any questions shoot me a message!
https://www.amazon.com/gp/product/B009AG12F2/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B004NXK60Y/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0002STSO4/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B01KVYH66U/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B000MY3ML8/ref=oh_aui_detailpage_o03_s01?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B00CTKBTH2/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

PS: Sorry for the pictures being all over the place. I had a hard time trying to get them on here.

[MN250R]

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[Arky-X]

Nice work, thanks for sharing!

What did you do with the reservoir for your master cylinder?
I thought I've read where others used one off a YFZ450 because it doesn't have a remote reservoir. I can't tell from the pics what that is.

[NeverLift]

249700249701249702

I have this if anyone wants to try and make it work. Came off an 03 400ex. I also have a stock header. Make offer. It's titanium!!!

[MN250R]

Nice work, thanks for sharing!

What did you do with the reservoir for your master cylinder?
I thought I've read where others used one off a YFZ450 because it doesn't have a remote reservoir. I can't tell from the pics what that is.

The brake resovoir is off a 450r Dirtbike

Like this one
https://www.ebay.com/itm/Rear-Brake-Master-Cylinder-Fits-Honda-CR250R-CRF250X-CRF450R-A-2004-/262651594587?hash=item3d2741475b

[DDQ]

What is the reason for using the aftermarket 450R silencer instead of the aftermarket 400ex silencer?
Also, would there be any performance reason to not use a stock 400ex muffler with the stock 400ex head pipe?

[MN250R]

What is the reason for using the aftermarket 450R silencer instead of the aftermarket 400ex silencer?
Also, would there be any performance reason to not use a stock 400ex muffler with the stock 400ex head pipe?

Not sure, that is just what i saw people have used in the past with good results. So thats what i went with :)

The 400ex silencer would probablly work also. Not sure where the brackets are located on it to bolt to the frame though.
I also believe it is because the 450r muffler is stainless steel where the 400ex isnt. Just my guess