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Message started by strang on 03/28/13 at 04:20:23

Title: welding a new exhaust - some advice
Post by strang on 03/28/13 at 04:20:23

I have a mig welder and have welded bit of frame tubing before (xs650).
I have a few days off coming up.
I want to have a go at welding up a new exhaust in the scrambler/street tracker style. I like the look but I also want to put mid controls on so hence the relocation.
I have a dyna muffler.
what pitfalls should I be aware of?
where is the best place to get supplies of pipe? local muffler place? what material - stainless? thickness?
should i use a sleeve over joins or just butt them up and weld the join? (my welding aint pro remember!)
any other advice much appreciated.

Title: Re: welding a new exhaust - some advice
Post by Dave on 03/28/13 at 04:45:58

I have no idea where you can get exhaust tubing on your side of the pond. Over here my favorite places are Burns Stainless and Megs Exhaust.
http://www.burnsstainless.com/
http://www.coneeng.com/motorcycle_components.html

Tig welding is supposed to be the best way to join stainless. Stainless welds are tough on a Mig Welder. The inside of the pipe reacts with the oxygen as you weld on the outside, and the inside of the pipe "sugars" and makes big drippy globs unless you run Argon sheilding gas inside the pipe as you weld. I have thougth that it might look good to make a stainless exhaust by using stainless slip collars over the joint - then using a brazing flux and rod compatible with stainless to sweat the collar onto the two pipe pieces to join them.

The other thing that you need is a collar to match the exhaust port that will be a large OD to fit the exhaust port and gasket - then a smaller ID to work with the pipe. For a stock engine 1.5" ID works good and then you need to adapt that to the 1.75" OD that slides into the DYNA muffler.

Title: Re: welding a new exhaust - some advice
Post by Cavi Mike on 03/28/13 at 04:53:10

For starters, you're not welding stainless with your mig because I know you don't have a spool of stainless wire in there and I highly doubt you're gonna drop $50 on a spool of wire just for an exhaust. Just get aluminized steel.

You might be able to get some scrap pieces of straight tubing from a muffler shop if you ask nice but you don't want any of their bends because they use crush benders. Aside from the obvious crushing of the piping restricting flow, it simply looks horrible. You need to get mandrel bends online.

Don't sleeve the exhaust, that's just an extra place for a leak. Bevel the edges of the pipes, butt them together and weld.

Title: Re: welding a new exhaust - some advice
Post by strang on 03/28/13 at 05:15:51

thanks this is real helpful. aluminized steel it is and I'll buy online.
sorry another question - is the existing pipe stainless? was going to use bits of the existing pipe so want to know if I can weld it with mig?

Title: Re: welding a new exhaust - some advice
Post by teabowl13 on 03/28/13 at 08:34:14

The stock pipe is not stainless, but it's three layers thick; a pipe inside a pipe inside a pipe... might be a little goofy to work with, but if you use the header portion and weld on the rest it might work for you.
Check out Lancer's posts, or just ask him directly; he's been working on a custom exhaust design, and he's worked out all the math and stuff...

Title: Re: welding a new exhaust - some advice
Post by Dave on 03/28/13 at 09:20:25

4273777479617A2725160 wrote:

The stock pipe is not stainless, but it's three layers thick; a pipe inside a pipe inside a pipe... ...

The stock pipe is only 3 layers thick where it necks down at the end. The other part from the header down to the outlet is only an inner and outer pipe. When I installed my O2 sensor I only drilled through 2 layers.

The stock pipe is chrome plated steel. If you are going to be cutting and welding on it - it is best to get the chrome stripped or sandblasted off first.

Title: Re: welding a new exhaust - some advice
Post by scubachef on 03/28/13 at 14:24:45

I did my own exhaust and used a muffler shop for the pipe. The header pipe was not a size that translated exactly into a size of pipe commonly available at least here in CA. I used 2"OD pipe with a 1.85"ID. It isn't exact...but really really close. Since the header pipe is layered you could sleeve the inside of the joint for a little extra strength similarly to the way a slug is inserted in the joint for a weld on a frame if you are not super confident with your welds. Normally that would be a big no no due to messing up the airflow but your pipe will be significantly wider than the inner pipe on the stocker so no ill effects I would think.

Title: Re: welding a new exhaust - some advice
Post by justin_o_guy2 on 03/28/13 at 16:44:26

There is an odd shaped part at the header/jug junction, inside the header. Its meant to halt reflected pulses. Have a look,,

Title: Re: welding a new exhaust - some advice
Post by strang on 03/29/13 at 13:00:39

This is what I've decided to do.
what's the best approach step by step to achieve this?
what angle bends are best to order?
blue box is where mid controls will sit.

Title: Re: welding a new exhaust - some advice
Post by justin_o_guy2 on 03/29/13 at 16:23:52

I think you would be miles ahead to take the bike & that printout to a shop & ask a pro to do what you cant & let you take it home & finish it,

Title: Re: welding a new exhaust - some advice
Post by scubachef on 03/29/13 at 19:00:29

Those are some tight looking bends. Definitely take the bike to a shop to have a new pipe bent. Sorry my earlier post is not really applicable, I thought you were still using most of the pipe and adding on. Have you thought about flow? I admit my experience is mostly cars, but those bends would be a performance disaster in a car application.