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Old 11-23-2019, 09:12 AM
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Default generic homemade exhaust pipe questions

All right guys. It's my turn to ask some of you guys some questions. Primarily to some of you guys that do a lot of your own fabricating. And I've seen some of the work some of y'all have done and it has been outstanding with the homemade frames and tube bending and what not.

I normally just buy a header from GPS and be done with it or use the factory muffler setup or just build a simple straight pipe setup which is easy enough to do.

My concern is not the welding but the bending. I don't want to tie up a pile of money into some kind of expensive tubing equipment if I don't have to.

I need to fab an exhaust for my 208 clone engine to go on the chopper bike. I plan. on using just plain old steel tubing sourced from Lowes. I already have several different sizes. I need it to come out and go down under the carb and come out and down the right side so it's going to take quite a few bends. I will probably just bend shorter pieces and weld them together for ease of fitment.

I know some people use the Harbor Freight pipe bender. Some folks have good results and some don't. I will NOT be using any type of heavy piping for any kind of exhaust work...it's just not suitable for the application I intend.

Exhaust fabbing and bending the exhaust pipes...what methods do you guys use, what do you guys recommend...tips and secrets...is the Harbor Freight pipe bender a usable tool or is there a better option at a reasonable price?
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Old 11-23-2019, 09:34 AM
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Got a ball hitch on the back of a truck? A buddy of mine mentioned that to me when I mentioned wanting a pipe bender, smaller pipe that will fit under the ball itself on the skinny area can be bent kinda using the hitch and reciever by hand. I'll probably be trying for myself soon, need a header for a gx390.
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Old 11-23-2019, 09:38 AM
karl karl is offline
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The hazard fraught pipe kinker, a usefull bit of kit, but has severe limitations.

It is a pipe bender, as in water pipe, not intended for steel tubing (Welded seam)

Water pipe is soft, thick, and malleable. Exact opposite of exhaust tubing.

I have used the hf kinker to build 2 minibikes, but with thick wall tubing. Packing it with sand will help it not kink, but no way it will bend thin tubing.

I think your best bet is to bring a cordless cutting tool to a lawn mower graveyard, and cut out some nice sections. Ask around, a repair shop might have some scrap pipes laying around.

I built this one from a mower bumper , and a cutoff from a kohler command for a big block clone.
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Old 11-23-2019, 10:20 AM
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In mine, I used EMT tubing. I found some sections and bends... I ended up pie cutting the bend and straight sections to form the look I wanted...
No bender, just grinder and welder.. a pen and tape helps.. but doing by eye is what I did..

If you do start a the engine flange first... Be careful about how you ground the welder.. not on the engine but the exhaust itself...
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Old 11-23-2019, 12:05 PM
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Quote:
Originally Posted by mckutzy View Post
In mine, I used EMT tubing. I found some sections and bends... I ended up pie cutting the bend and straight sections to form the look I wanted...
No bender, just grinder and welder.. a pen and tape helps.. but doing by eye is what I did..

If you do start a the engine flange first... Be careful about how you ground the welder.. not on the engine but the exhaust itself...
I have actually considered this, thought about mocking something up with a wrapping paper tube and using that as a template.

I am curious as to how geometric appearance would be. I want it more smooth than angled looking. You know stuff like this would be simple if those stores carried prebent 45 an 90 angles I could just weld in. Then I could make anything I wanted.
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Old 11-23-2019, 12:12 PM
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......Maybe you could just buy a kit from BMIKarts:https://www.bmikarts.com/Exhaust-Hea...Kit_p_893.html
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Old 11-23-2019, 12:32 PM
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Quote:
Originally Posted by Smerft85 View Post
Got a ball hitch on the back of a truck? A buddy of mine mentioned that to me when I mentioned wanting a pipe bender, smaller pipe that will fit under the ball itself on the skinny area can be bent kinda using the hitch and reciever by hand. I'll probably be trying for myself soon, need a header for a gx390.
Yes, I tried that for something else but it failed...kinked...

---------- Post added at 01:32 PM ---------- Previous post was at 01:14 PM ----------

Quote:
Originally Posted by JTSpeedDemon View Post
......Maybe you could just buy a kit from BMIKarts:https://www.bmikarts.com/Exhaust-Hea...Kit_p_893.html
I could do that, and I may, but I probably wouldn't be happy with it cause it doesn't have what I need to do what I want...not all...but I will leave it on the table.
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Last edited by BigWes; 11-23-2019 at 12:24 PM. Reason: Stupid phone autocorrected and changed what I wrote
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Old 11-23-2019, 08:27 PM
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Quote:
Originally Posted by BigWes View Post
I have actually considered this, thought about mocking something up with a wrapping paper tube and using that as a template.

I am curious as to how geometric appearance would be. I want it more smooth than angled looking. You know stuff like this would be simple if those stores carried prebent 45 an 90 angles I could just weld in. Then I could make anything I wanted.
You could go the template route... Id think itll get kinda awkward trying to replicate in this manner.. Thats more or less why I went free hand on mine... you make it fit as you go.. Im sure they make pre bent elbow/bends..
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Old 11-23-2019, 08:49 PM
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I used to build a lot of turbo headers and systems, I’d order mandrel bends and cut and splice them to get what I needed and then tug weld everything.
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Old 11-24-2019, 05:19 PM
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Cut out and save any bends from anything I throw out. Leave about 12-18" of tube on each side. Maybe a little more on one end.

My drift trike project has a pretty wicked looking dual chrome exhaust on it made from a barstool. My rat rod wagon has a long side dump exhaust made from an air hose reel and a futon frame. My budget build kart exhaust is barstool and roto tiller handle. And they all look pretty darn good.
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Old 11-24-2019, 07:38 PM
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That's pretty cool...never even considered hacking up old chairs and stuff...

Been out of town the entire weekend so I've got nothing done.

On a good note my buddy gave me an old predator 301 he had stuck out in the barn that didn't work on his tiller. Still in the box. I guess I can use it for something.
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Old 11-24-2019, 09:23 PM
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If you accumulate a big enough assortment of tube, it's pretty easy to piece together whatever shape exhaust you want. Most of mine step up diameter as they go, using sections that sleeve into each other, with a thicker wall nearest the engine to minimize vibration.

Doesn't help much if you're wanting to build something right now, but in time, it's a great way to go.
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Old 11-25-2019, 05:45 AM
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I can tell you more than then you need.

pipe and tubing are two different sizes, you need the right size die to make the bends you require.

muffler shops only have certain size bender dies.

flex tubing can be used??

straight tubing, make angle cuts, no bending required.

with a JD bender you will need to have the dies for pipe or tube and every time you change size, tube thickness from a spark plug gap to .063 th. wall will be good.

Kartcha ya later
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Old 11-25-2019, 11:49 AM
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Those JD benders are sweet I seen some guy showcasing one on YouTube but just one set of dies are expensive as the basic unit...but it does nice work.
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Old 11-26-2019, 06:41 AM
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I am faced with the same dilemma on my kart build and have chosen to buy straight and bent pipe(tube) and weld it together. Biggest issue is the diameter is so small it is not common/standard. Luckily after hunting around I did find enough bends to do exactly what I want. I only have a starter pic at the moment.




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Old 11-26-2019, 10:37 PM
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I'll show you guys what it's going on as soon as I get a chance...I just been busy as heck
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Old 11-28-2019, 08:49 AM
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Default I used auto sections, max flow, min noise.....

I made a custom exhaust for a 212 that was almost free flowing and quiet as a new lawnmower. Used 3" x 18" exhaust extension from auto parts store, cut into sections, welded on sheet metal as "end pieces" or "bulkheads", pierced from one to next with 1.5" pieces, welded all solid. Ended up with 3" x 13" canister with 1.5 - 5 - 5 - 1.5" sections (5 "bulkheads total").
Had exhaust switching 180 degrees 4 times internally, almost unrestricted, came out shockingly quiet due to "noise cancelling headphones" principle. Fed from a blank exhaust flange to canister with 1" EMT conduit pie-sliced and welded solid into the bends I needed. Best of both worlds on performance and noise.
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Old 11-28-2019, 06:13 PM
mckutzy mckutzy is offline
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That is cool... Id like to see this... pics if you have them...
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Old 12-03-2019, 10:28 AM
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Default Here's that exhaust........

Here you go mckutzy, pics of the custom exhaust, and sketch diagram I started with. Note that supporting U-bolt is piercing 2 balls of S.S. wool to give support but allow for vibration and the rubber motor grommets. Rock rigid would eventually snap the 1" EMT flange-to-canister inlet pipe.
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Old 12-04-2019, 05:53 AM
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That's pretty cool. I have been tossing muffler ideas around for a while, but this looks really good. Any estimates on sound level vs stock muffler on predator?
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