Newbie Q: Fix for crushed header pipes?
ed b
Newbie question here. Anyone have any ideas on how to repair
crushed header pipes? My motorcycle has a 4 into 1 header on it
that got tweaked. I'd really like to avoid shelling out $300
bucks for a new header and I like the idea of fixing something
and learning a little bit at the same time.
The damage is where the headers bend back under the bike, right
before the collector. Imagine that you ran the bike into a curb
and it flattened the 4 pipes where they pass under the engine.
And no, I didn't hit a curb and smash them, they came that way.
Not that I haven't hit or smashed plenty of things, I have, just
not this particular damage. :^)
The individual pipes are now in the shape of a "D". With the
muffler removed I have access to the bent areas, I just don't
know how to round the pipes out. I was thinking of trying to
heat them up and somehow expanding the pipes from the inside
out.
One suggestions was to fix a steel ball (that has a diameter
slightly smaller then the pipe inner diameter) to a metal rod,
heat the pipes up, then bang the steel ball into the pipes,
slowly expanding the pipes from the inside out.
Some questions are:
How much heat would it take to allow me to bend the metal? Does
the metal need to be "red hot"? I was told that I would need an
acetylene torch, that a small propane torch would never do it.
How about cooling the metal? Air cool it, or dunk it in water?
Unfortunately I don't know the steel guage or grade, but its a
typical motorcycle exhaust. And I don't really know anything
about welding and joining, but I'm a quick learner, and pretty
good with engines, motorcycles, etc. And I have a friend that is
a welder, he has an acetylene torch if I need to go that way.
Any tips, tricks, insights, or mild abuse for a stupid idea
welcomed!
Thanks,
Ed
Duvall, WA
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timerak
for sealing both ends of the pipe, then slowly filled it with high pressure
water. It popped right out. The high pressure water source was from a
hydrotest machine at an industrial plant. Something like a pressure washer
would work. The key is to do it slowly!
ed b wrote in message <084f42aa...@usw-ex0105-036.remarq.com>...
czr...@powerup.com.au
>One suggestions was to fix a steel ball (that has a diameter slightly
>smaller then the pipe inner diameter) to a metal rod, heat the pipes up,
>then bang the steel ball into the pipes, slowly expanding the pipes from
>the inside out.
That's not such a bad solution. I'd advise you to remove the header from
the bike and fix it to a solid work table. There's going to be a lot of
heat and vibration, and you don't want to do any further damage.
>Some questions are:
>How much heat would it take to allow me to bend the metal? Does the metal
>need to be "red hot"? I was told that I would need an acetylene torch,
>that a small propane torch would never do it.
A _small_ propane torch wouldn't be sufficient. At best you'd only be
able to get a small area to the right temperature. Heating is all about
BTU's. You have to put more heat into the area than you lose by
radiation, convection, and conduction. Heating a 2" section of pipe that
is part of larger piece takes a lot more heat than just heating a little
2" piece of pipe.
>How about cooling the metal? Air cool it, or dunk it in water?
Definitely air cool. Quenching is used for heat treating and by the
impatient.
>Unfortunately I don't know the steel guage or grade, but its a typical
>motorcycle exhaust. And I don't really know anything about welding and
Low grade stainless steel (often 304) in about 16 guage is used. Tuned
headers use a thicker pipe than the single exhaust.
Many stainless steels harden with cold working, so it's important to use
the right heat and not too much force. If you harden the header pipes
they could crack from vibration, or corrode faster.
>joining, but I'm a quick learner, and pretty good with engines,
>motorcycles, etc. And I have a friend that is a welder, he has an
>acetylene torch if I need to go that way.
You'll also need a heating rosebud by preference. A small one would do.
I'd say #6 but that's a metric size.
If he doesn't have a heating tip, you might get away with using the
preheat on a larger cutting tip.
>Any tips, tricks, insights, or mild abuse for a stupid idea
>welcomed!
It's not so silly, if it saves you $300. Actually it won't save you all
of that, because you'll use a bit gas.
Don't put too much heat in one area - move the rosbud around a bit to
spread the heat.
You'll find it might take a little time to heat the area because heat will
be lost in conduction. Once the part is generally warm heating will be
faster.
For stainless steel you'll need to get the metal to a moderate red heat.
Don't use too much force, apply more heat instead. Don't heat the pipe to
yellow because if you do you'll start oxidising the chrome out of it, and
cause other reactions that will make the metal brittle. Stainless steel
has a higher melting point than carbon steel and it's unlikely that you'll
melt the metal unless you really overdo it.
Take your time. If you try to do too much in one go you will crease the
metal.
It would be better to have two people to do this - one to apply the heat
and the other to work on the header.
Afterwards, wire brush and/or polish the pipe. This will remove the
surface layer of chrome oxide caused by the heating and restore the
corrosion resistance. Acid pickling can also be used. If you don't do
this you might find the pipe corrodes rather more quickly.
Good luck - you might find fixing the header improves engine performance
by a surprising amount, so it's worthwhile.
--
Regards,
Chris.
-----------------------------------------------------------
czr...@powerup.com.au <Chris Robinson>
Brisbane, Australia
-----------------------------------------------------------
Welding Information Site:
http://enterprise.powerup.com.au/~czrobin
AAsberry
>
>Newbie question here. Anyone have any ideas on how to repair
>crushed header pipes? My motorcycle has a 4 into 1 header on it
>that got tweaked. I'd really like to avoid shelling out $300
>bucks for a new header and I like the idea of fixing something
>and learning a little bit at the same time.
>
>The damage is where the headers bend back under the bike, right
>before the collector. Imagine that you ran the bike into a curb
>and it flattened the 4 pipes where they pass under the engine.
>And no, I didn't hit a curb and smash them, they came that way.
>Not that I haven't hit or smashed plenty of things, I have, just
>not this particular damage. :^)
>
>The individual pipes are now in the shape of a "D". With the
>muffler removed I have access to the bent areas, I just don't
>know how to round the pipes out. I was thinking of trying to
>out.
>
>One suggestions was to fix a steel ball (that has a diameter
>slightly smaller then the pipe inner diameter) to a metal rod,
>heat the pipes up, then bang the steel ball into the pipes,
>slowly expanding the pipes from the inside out.
>
>
>How much heat would it take to allow me to bend the metal? Does
>the metal need to be "red hot"? I was told that I would need an
>acetylene torch, that a small propane torch would never do it.
>
>
>typical motorcycle exhaust. And I don't really know anything
>good with engines, motorcycles, etc. And I have a friend that is
>a welder, he has an acetylene torch if I need to go that way.
>
>welcomed!
>
>
>Ed
>Duvall, WA
>
The wall thickness may be heavy but I would talk to one of the paintless hail
dent repair places.
Andy - Prescription without diagnosis is malpractice. In medicine and
mechanics.
You know the true e-mail address.
Jeff Homolka
<edbNO...@onyx.com.invalid> writes:
> Anyone have any ideas on how to repair
>crushed header pipes?
A mashed pipe is a common occurance with 2 stroke dirt bikes.
The same method would probably work on your header.
What you do is pressurize the pipe with air. I use 40 psi or less.
With the pipe pressurized you heat the dent with a torch to red heat.
The air pressure will push the mashed part back into shape.
I've done lots of this kind of repair. It works real slick.
A few pointers.
I use a small pressure regulator on the input air line.
This regulator needs to be able to bleed off pressure that builds up as
the pipe heats up. Use a guage that will read pressure from inside the pipe.
When heating the area of the dent it's usually best to work from the edges
inward toward the worst dammage. If the mashed area has a kink in it,
it will likely be a problem. Try to work the kinked part out first.
Don't use an expanding rubber plug to seal the end of the pipe.
It's likely to blow out like a champagne cork. To plug off the pipe
for holding pressure I made a fixture with a ring that secures around
the pipe with set screws. The ring has a bracket with a long screw
that holds a rubber backed plate to the end of the pipe.
If you imagine how a gear puller attaches you will get the idea.
In fact some small gear pullers may be good for holding caps onto
the head pipes instead of making fixtures.
You might consider brazing or soldering caps onto the pipe ends to seal them.
If these are stock pipes they are probably double walled and that would
certainly make things more difficult.
Good luck
Jeff
ed b
right track. I'm going to talk to my welding buddy and see if we
can't give this a shot. Sounds like patience is key.
ed b
heavy. Might be worth a call though. Thanks.
ed b
place in Oregon, but they told me they only do 2 stroke pipes,
not 4 stroke ones. They didn't say why, but I'm thinking its
because the 4 stroke pipes use a heavier guage steel.
ed b
leaning towards the heat and bend method.