Check out the sale thread on Moped Army at,3563558


NOTE: This sale thread will be interactive: I’m gunna update you the whole way though.

I’m starting work this morning on a custom expansion chamber. The dimensions are very close to a Puch Proma Circuit, but this chamber will be straight. It will be made from 20 guage mild steel, it will have 4 cones, and will be pretty darn light. If you want the same tuned length, you’ll want 200mm of header on this guy. It can be rear-bled or side-bled – I’m keeping both options open until someone wants to claim it.

Price? This is new to me. Not building pipes, but selling them. If you want to give me $80 for the chamber, it’s all yours. if no one wants to pay $80, I’ll take the highest offer tonight. For another $40, I’ll also make you a baffle.

The baffle can be the standard aftermarket free-flowing design using packing for sound deadening, or a more OEM style packing-less design. Free-flowing will get you a couple more RPM, OEM style will get you zero maintenance and slightly more back pressure.

Want something custom but to your specifications? Get at me. Lets make it happen.


here’s a time-lapse of another build. Sorry, no time lapse on this one, but I’ll add more post with pictures as it progresses.


Here’s where we’re at right now. These are YOUR templates cut this morning:


Maize BLK Wrote:
> What do you cut the steel with?Left and right handed shears and I’ve also added some electric nibblers to my arsenalNow we have cardboard templates (dont tell the post man….):




We’re one step closer ladies and gentlemen. Got some interest, but its still up for grabs!


Chris Toth Wrote:
> Do you roll your own cones? If so, what kind of
> tool do you use?

They’re hand rolled and banged out over a steel pipe in the vice. here’s where the magic happens:




One cone tacked up:




Jeremy Husk Wrote:
> Very Nice work! Not only the skill it takes but my
> god man the patience this would take lol

Thanks Jeremy! That’s just it. Patience. And you gotta be ok with failing a few times before you get it right.

I’d much rather see guys makin their own stuff than buying mine. If you have questions, ask away!

You’re watching this happen as I post

Cone Número Dos:




A one, a two, a three…




And here’s the concave cone. Take a look at that tip!! It’s the harderst part (and kinda unnecessary, honestly) because it’s just you, a steel hammer, and a flat surface. I dont have anything to hold the shape that small.




Chris Toth Wrote:
> What’s your welding setup? Tig?

I wish. I’m just using a 110 volt wire flux welder.

I scored mine a few years ago for $150 on craigslist with a $60 roll of wire in it. It’s called a Century Quick-Fix welder. It’s very similar to most of the cheapos you find in non-welding stored except it has a couple key advantages. It outputs DC instead of AC and it’s fan cooled. It’s easy to weld with it, it’s not easy to weld well with it. You gotta have a good, clean tip that fits the exact size of wire you’re using, keep a good ground on your part, and dial in the feed until it’s just right. I’ve also bought every type of wire I could buy locally (5 or 6 kinds) and they are Verrry different. Even if they’re the exact same spec (by welding codes/standards) each brand is a little different. By far the best wire I’ve found is Lincoln’s E71-T11. I dont lay down dimes. Sometimes i come close, but I prefer to make sure I get good penetration and clean it up with a finish grind.




Dillon Ryan Wrote:
> No center dwell section?
> Coming from a fellow Flux Core MIG welder
> (Millermatic 180), you’re doing it right and
> getting very good results.
> Interested to see this pan out

Thanks Dillon. I was welding without any finesse for what seemed like forever and I always assumed it was just the welder. Then I realized, like anything else, there was a right and a wrong way to do it.

Nope, there’s no dwell on this guy. Theory and practice clashed on this one for me. I tried many 7-8 cone pipes with a dwell section, and this design right here trumped it every time. a straight shot to the dwell section made more power than tapering out to the dwell. Then the long-ish (200mm) converging cone spreads out the powerband over 3500-4000 rpm. I worked really hard making pretty pipes that didn’t measure up to this thing in terms of power.

Now, all that testing was done on a piston port cylinder. I think there might be some other advantages to more round looking pipes when you have reeds and your reeds slam shut and very your intake timing with rpm.

Whoa. Almost got lost in theory again.

Off for a quick blast on the champ and back to welding!


One step closer :




My leather apron is one of my all time favorite purchases. It’s already saved so much of my clothes.








Cleaned up




mike murphy Wrote:
> What gauge steel are you using?

20 gauge

It’s slightly thicker than most stock pipes and hydro-formed aftermarket pipes, but thinner than most other custom stuff you can get your hands on. If you want to blast with the same pipe for years to come, it might be too thin for you. If you want the lightest custom pipe you can get your hands on, I think this is the ticket.

I hope to keep it affordable enough it won’t break your heart if you smash it up and need a new one.


This pipe is still up for grabs as of today (December 19th)

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