[RideRed04]

Like I said, I did this on a 400ex, but I dont think it is very different for a z400.

I was looking for a little free power, so I decided to mod a stock exhaust. I asked if anyone wanted to sell one for cheap in the classifieds, and ended up getting one for free.
Getting started
Things you need:
 A welder
 Something to cut open the exhaust
 A hack saw
 Drill press
 An 8mm socket or wrench
 Some high temperature paint
 Gloves
 Some eye protection.
I used a dremel to cut it open, but a sawsall or hacksaw would probably work better.
First things first
One little tip that will help you out later on is to take a scratch awl or other sharp instrument and scratch some lines in the front of the silencer so you can line it up later. First, unbolt the three 8mm bolts holding on the baffle and clamp the exhaust into a drill press. I drilled 4 ½” holes into the plate inside the exhaust. Another way of doing this is to turn you welder way up and turn the wire feed way down to burn through the metal.
Getting dirty
Now for the hard part. Cut open the exhaust where it angles from the head pipe to the body of the silencer. Once you cut through there will be a pipe inside, and you will need to cut that off too. Once that is cut off you need to remove a 2” section of that pipe.
Getting it all back together.
This is where the scratches come in handy. You can line up the marks so it will be strait when you put it on. I used duct tape to hold it together while I tacked some weld on. After it was sturdy, I put a bead all the way around. When you are welding thin metal, you need to turn your wire feed up to keep the metal cooler; otherwise you will burn through.
Finishing touches
Now it is time to paint. Find a nice dry place to paint. Make sure you use high temp paint so it doesn’t bubble off. I used black, but you could use any color you wanted to match your quad. After the paint has dried, polish up the baffle with some paper towel while it is off. If it is really bad, now would be a good time to get some regular metal polish on it and clean it up good. Bolt that back on and make sure the bolts are good and tight.
Congratulations!
You have just gotten yourself a free aftermarket exhaust that is much quieter then other systems, but still has a better sound then stock. I am not using the exhaust on my quad, but have driven the 400ex that it is on, and it seems to make a noticeable difference in low end power, and sounds much better then stock. It was a very rewarding project, and gives you the ultimate sleeper quad, perfect for sneaking up on unwary 4-wheelers.

 

[sduncan]

I did something similar on my EX but I don't know if the same idea is possible for the Z. Heres what I did on my EX:
After removing the silencer from the quad go ahead and remove the 3 8mm bolts and pull the spark arrestor.
Towards the front of the silencer you will see some spot welds that the factory made. Using a 14in chopsaw, cut the silencer in half just in FRONT(meaning towards the front of the quad) of those spot welds. It helps to scratch or centerpunch 2 marks on either side to help re-align the halves later.
Using a Dremel or a small cut off wheel, cut the pipe off as far down into the "cone" or "funnel looking piece" as you can When you look into the cone shaped piece you'll see the part that needs to be cut off.
Next, using a drill bit in the large variety(13/16,15/16/or 1") drill three holes in the inside canister from the back as if you were looking into the silencer from the back. Your bit should be long enough to reach in and drill the holes . The metal is not thick. Do try and line up the new holes w/ the tubing that runs thru the inside canister.
Next put the spark arrestor in the chopsaw and cut it off at the metal band. You can save the wire mesh if needed and braze it back on the end cap.
Using a wire feed, weld the two halves back together and grind the weld smooth w/ a flexible gring wheel. Paint w/ high heat black and put it back on. Mine took me abou 1.5 hrs. start to finish. You'll also want to grind down the welds in the header. Pull the header off and look into the tubing. You'll see that the welds in the header choke down the I.D. of the tubing. Use a stone and grind them down to the same size as the tubing Add a uni, cut the front part of the snorkle off(under the tank) to open up the hole bigger, add 6 uni 1" vents to the airbox and go to a 152 main and you'll be happily impressed. Total cost of around $35.00.

 

[flaneledholes]

Thanx for posting, I was eondering if it could be done on the Z or not... I know the 400's exhaust flow goes something like this, excuse me for the crappy example...

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Get the idea???