How To : Remove Restrictions In Aftermarket Pipes

[90GTVert]

Removing The Restrictors From Aftermarket Exhausts

This particular pipe is a Leo Vince ZX designed for 100cc minarelli engines, but many other companies, and sometimes the manufacturer of the scooter, install similar restrictors to meet Euro approval or whatever standards they need to comply to.

Restrictor 1

Restrictor in the head pipe.



I ground the spot weld until it was nearly free and then wiggled the restrictor loose.



Here's the restrictor.



Once it was out I just ground the spot weld out so the header was smooth.



Some people use a chisel to knock out the restrictor. Whatever method you choose, be sure the restrictor isn't going to fall inot the pipe and I suggest smoothing out the weld that you break/grind/cut off.

Baffle Sound Deadening

I hesitate to call this a restrictor, but it is unnecessary material inside the pipe. Removing this will make the exhaust louder and didn't seem to increase performance any in my case. Unless you are making sure you squeeze every last bit of power out of your scooter or you want a louder exhaust, you may want to skip this one.

Remove the silencer and brackets from the pipe.



Cut the pipe in two at the weld just behind the mounting bracket.





You should see a perforated cone in one end. This is held in by a few spot welds. Grind or chisel out the spot welds and you should be able to remove the cone.





Now remove the sound deadening material that's left in the exhaust.





If your pipe has carbon buildup, clean that out. Otherwise, weld the pipe back together and reinstall the silencer and brackets.



Opening Up The Header

Some aftermarket pipes have a tube installed in the end of them that will hold a ring style exhaust gasket into place and make installation of the exhaust a little easier. That's nice for convenience, but may not be good for performance. For smaller engines, this may not be worth the hassle. I'd suggest comparing your exhaust port diameter to the inside diamater of your header before attempting this, and then deciding if the change is worth it. In my case, the ZX for 100cc Aerox is restricted to only a 21mm inlet ID because of this ring, and I was looking for much more than that for this engine.



After trying to chisel out the piece, I discovered it was welded all the way around and chiseling it out wasn't a good option. I cut the flange off and worked on it that way instead. Here's the pipe side. What was left there popped out easily.



Here's the mess I made of the flange side with a chisel. I think an easier bet may be to simply grind this ring out. It takes time, but so does cutting and re-welding. The big advantage to cutting and welding is that it gives you a good chance to port match as I show in a moment.



I ground that out and ended up with a 26mm flange, up 5mm from before.



I decided not to weld it back together until I match up the cylinder. This pic illustarates why that's a good idea in this case. It is worth checking this while you have it off if you end up cutting the header flange off as I did.



With a little grinding in both of the slots it lined up much more evenly.



I used washers too small, then drilled them to a size where the bolts would just fit through without scraping the threads (15/64" worked well for my M6 bolts) for a very snug fit.



Bolted the flange back up with one washer in place. Stuffed the cylinder with wet rags to keep any slag outta there and tacked the washers in place. Then removed the flange, finsihed welding, and filed it flat.







Repeated for the other side and now there's really no room for movement so I can be sure it stays where I want it after it's port matched. It's not pretty, but it should work.



A little time with a Dremel and you can really see the improvement.



I figured I better bolt up the flange and get everything lined up rather than just welding the flange back on as it was. Probably a good idea since it didn't line up at all in it's original position.





Ended up pulling the exhaust in toward the tire more, but there's sufficient clearnace.



I welded it inside and out. It's basically finished. I just need to finish sanding the inside and repaint, but I ran out of sanding drums.





So there you have it. With the use of the alterations above, you might turn an average pipe into a great pipe. ;D

[Ronan Alves]

Hey guys,

i will show to you the new way that i found to unrestrict the second part on a leo vince exhaust.

i saw here a brent way to unrestrict but i dont want cut my entire exhaust and dont want have a big weld on it.

Than i have and idea here, we only make a big hole inside of the exhaust ( on the tire side) and cut the entire metal inside to take it off.

look the pictures.

[90GTVert]

Images showing the silencer restriction in some Yasuni exhausts and it's removal by grinding the welds around it.

Nov 11, 2015 1:30:50 GMT -5 Lucass2T said:

Nov 11, 2015 5:23:38 GMT -5 Lucass2T said:

Just undo the two nuts, slide silencer off, take cap off and grind out the welds.

[90GTVert]

Oct 9, 2016 19:33:41 GMT -5 lobarrett said:

Dec 9, 2016 6:20:10 GMT -5 lobarrett said:

My 50cc ET2 Build Project - Removing the Restrictor

Armed with all the above knowledge it was time to undertake the task.

The only restrictor I had to worry about was the one welded into the engine side of the exhaust flange. And, as I stated earlier, I thought this would be a good task for my Dremel. So when I had sometime, I grabbed the Dremel, my favorite attachment the EZ 1 1/2" cut-off wheel, the next R pipe and headed out to the back of my truck (tailgate workbench). That's when I realized that a new 1 1/2" cut-off wheel was just to big to fit the small diameter pipe - so I got a well used one and started to make my first cut which ran into the flange. So the EZ type cut-off wheel wasn't the right attachment.

"This little restrictor is made to stay in the pipe - one extremely hard weld to grind out"

I had other mandrel type cut-off wheels and the Dremel 409 15/16" Cutting Wheel looked like the perfect wheel - only problem - I could not get the screw out of the mandrel. I needed something else. It was going to be a good time to check out some of their other attachments. So I grabbed what I had and headed back out to the truck.

Here's what I tried:
Dremel Attachment List
1-100 High Speed Cutter - for use on wood, plastic and soft metals.
2-84922 Silicon Carbide Grinding Stone - sharpening, deburring and general purpose grinding on harder materials.
3-7105 Diamond Point - wood, jade, ceramic, glass, hardened steel, semi-precious stones and other hard materials.
4-545 Diamond Wheel - cutting, sawing and carving of hard materials, such as marble, concrete, brick, porcelain, ceramics, hard epoxy and soft and hard wood.
5-953 Aluminum Oxide Grinding Stone - general-purpose grinding on metals, castings, welded joints, rivets and rust.
6-9901 Tungsten Carbide Cutter - shapes, smooths or grinds especially hard materials including: hardened steel, stainless steel,
cast iron, nonferrous metals, fired ceramics, plastics and hard woods.
7-EZ406 EZ Lock™ 1-1/2" Cut-off Wheels - Metal cut-off wheel
8-426 1-1/4" Fiberglass Reinforced Cut-off Wheel - cut bolts or screws or make slots in rusted or stripped bolts -
9-409 15/16" Cutting Wheels - cutting metal with limited use on wood and plastic.

And, Here's what worked and what didn't.

Dremel Usability Chart

Attachments 3, 4 and 5 might have worked but it would have been slow going - too slow for me.

I ended up using the "Tungsten Carbide Cutter" - It's load and will scare the crap out of you, but it did a fast and reasonable nice job. Used a Dremel drum sander attachment to clean up the pipe and flange.