Topic: Aluminum pipes on stock downpipes?

[Alan F.]

I'm working on a low dollar CM400 project and my stock exhaust leaves me wanting something more. The mufflers have a few holes that I can patch and all and the crossover canister is in decent enough shape, but here's what I'm thinking....

I've got a good pair of stock downpipes, I also have several 20" lengths of 1/8" wall aluminum tubing.  I can join a few sections of this tubing with HTS-2000 brazing rods and couple them to the downpipes. I'm planning a nice hidden crossover pipe too. I've got a small lathe and I can spin up some end caps and make up several different types of baffles....one certain to work with my stock jetting.

The question is will aluminum be safe to use as an exhaust pipe? I've read about copper producing dangerous chemicals when uses as an exhaust pipe, but nothing about aluminum.

I know there are tons of slip-on mufflers made from it, but I don't know about any pipes.

Does anyone have any thoughts?  I'm hoping to drop about 30 pounds from the bike this way between crossover canister and stock mufflers.

Thanks.
-Alan

[BlindJoe]

Seeing as the thermal expansion of Al is twice that of steel, I don't think the joints would last too long due to the stress caused by multiple heating/cooling cycles

[Alan F.]

Well considering that I'll be using stock downpipes and the aluminum parts will all be straight shots without any bends....I'll give it a shot.
I might add a crossover tube, which could cause issues with thermal expansion and fatigue, but I'll be able to hear the difference when that happens and swap out to a different set of pipes if needed.

I can only conclude that if it were a useless gesture to use aluminum, there would be no slip-on mufflers made from the stuff for any type of bike.

[BlindJoe]

Yeah you might as well give it a shot, it may end up working, as you know theory and practice aren't one in the same. It's not like failure would be life threatening and I'm sure it'll look a hell of a lot better. Keep us posted  

There may be aluminum mufflers, but how many aluminum headers have you seen?


On a diff. note you wouldn't have any desire for a rechromed front/rear fender or chainguard that have been collecting dust the past 5 yrs, from an '80 CM project that never came to be, would ya?

[Alan F.]

Thats what I'm thinking too.   Aluminum headers, no probably not. The first bend would receive tremendous heat and pressure and would certainly crumble and blow out in short order.
Here are a few mock-up pics I took this afternoon. I'm digging the long straight pipes and will probably build a set, but the short alum. extensions replacing the crossover chamber with a simple H-pipe are the general plan.  I wonder what diameter the crossover needs to be?
I think a little research is in order, I've seen automotive H-pipes where the same diameter tubing is used for the crossover as the pipes themselves...but I've also seem CMX450 pipes where the crossover is more like 1/2 to 2/3 of the pipes' diameter.  Hell I could probably thread in some brass compression fittings and use a fat brake line for a crossover...
I've flat blacked my rusty tins on this bike, the tank on it is garbage too, a buddy has a yellow Hawk tank I'll be using. Thanks for offering the rechromed bits though I'm a bit far and this bike's a semi-rat, maybe offer them up at the hondatwins sites? (.com and .net) lots of us here go there too, familliar names everywhere.
-Alan

oops forgot pics...

[BlindJoe]

any updates?

[FrankenFrankenstuff]

I was thinking about trying to make a copper header. Or what about one made out of electrical conduit? Copper would be badass....and you could get all of your supplies at Lowes. The cost would be about the same as a MAC....but the coolness factor - priceless.

[Alan F.]

There is danger involved in using copper as an exhaust materia. i remember reading somewhere (maybe in here somewhere) that there was a race team way back when who used copper for their exh systems...they all wound up having the same medical issues in short order and soon all died from the same cause... something about the chemistry of the exhaust gasses reacting with the copper to produce something nasty and toxic. please search for it and be careful.