How important is the exhaust crossover pipe?

[Guest]

It didn't go any higher or lower, just the cadence changed.

Because of the crossover, if you listen to the end of either pipe (let's pick the left one), you will hear a bang when #3 fires through both pipes, then a BANG when #1 fires through the left side only, a bang when #2 fires through both pipes, then nothing as #4 fires through the right pipe. Of course, the right pipe does the same thing, but oposite in the firing order.
Listening from the middle at the back, you would hear:
...(left) ... (right)
3. bang .... bang
1. BANG
2. bang .... bang
4..............BANG
3. bang .... bang
1. BANG
2. bang .... bang
4............. BANG

After removing the crossover, you would hear:
BANG
BANG
............ BANG
............ BANG
BANG
BANG
............ BANG
............ BANG

It is just a subtle difference, but that is what made it sound like a Suzuki. The new cadence is what they sounded like before 1980, so it's nothing new or radical.



Check with your local auto parts store(s) to see if they have any pieces of 1 1/4" exhaust tubing. Stores around here used to carry them, but now don't carry anything smaller than 1 1/2". The pipe you want will be flared at one end for a slip fit onto another pipe. If you find them, they will likely be 18 or 24", you will have to cut them. If you can not find any in a store, go to a muffler shop, have them cut two pipes for you and expand (flare) one end. You need two pipes that are 7 inches long. I tried 7 1/2" to make sure they overlapped at the joints, but had problems with the excess length.

Here is what they look like. You will also need to cut four slots in the flared end to give it room to clamp down.

Here are the new pipes clamped to the downpipes with the original clamps:

Here is why I had to come up with this repair:

I have done this to two of my bikes and at least two others, so I know that it works well.

.

Steve, with this setup are we eliminating the exhaust gasket material then

 

[Guest]

Probably not necessary. You could probably do the same thing on the other end with crossovers on the sync ports between 1-4, 2-3, on the carburetors. It does make a small difference , especially in low end. Triumph and others have done the same with their carburetors.

 

[Steve]

WOW!!! Yet another thread that has been lying dormant for almost a year and a half has been brought back to life. :encouragement:

Steve, with this setup are we eliminating the exhaust gasket material then

That depends on how tightly your pipes fit. Mine were loose enough that I re-used the gasket from the old pipes and pieces.

.

 

[Guest]

WOW!!! Yet another thread that has been lying dormant for almost a year and a half has been brought back to life. :encouragement:



That depends on how tightly your pipes fit. Mine were loose enough that I re-used the gasket from the old pipes and pieces.

.

My old gaskets are fell apart, should I adjust the pipe size I guess is the question. Probably should take the pipes to the exhaust shop

 

[Steve]

Just ask for a couple of pipes that are 1 1/4" diameter, 7" long, have them expand one end for about 1 1/2-2". Expand it just enough to slide the other pipe in. When you get home, use a hacksaw to cut some slots about 1" deep on the expanded end, then slide everything together and clamp it up. If your stock clamps are still good, use them. They take a LOT less room than a typical muffler clamp, which will hang down below the bike and get damaged by road debris.

Print out the pictures to show them what you are trying to do.

.

 

[Grimly]

Probably not necessary. You could probably do the same thing on the other end with crossovers on the sync ports between 1-4, 2-3, on the carburetors. It does make a small difference , especially in low end. Triumph and others have done the same with their carburetors.

Supposedly the reason for the YICS system, that I've been blessed with on the XJ - only means I have to acquire a special tool now to set the carbs up. Blocks to them.

 

[Brendan W]

At one time Honda said that 40% of all their computer time in r&d was on exhaust tuning. The general idea was to have the shock waves from an exhaust valve opening reflected back to another exhaust valve at just the right time to reduce spillover of fresh charge air before the valve was physically shut. Crossing and fitting joining pipes gave more possible pathways and flight time durations for this effect to happen. I imagine it was more important for two strokes. The Z650s had some models with crossed headers as Steve mentioned which if you believed the published graphs gave a bit more mid range torque at the expense of a bit of top end. I had one of those crossed 650s and replacing the exhaust the only difference I could tell was the sound.

 

[JEEPRUSTY]

[FONT=CG Omega,Arial]William Carlos Williams, "so much depends"[/FONT]

---

so much depends
upona rusty crossover
pipe
glazed with rain
water
beside the white
chickens.
​

 

[Brendan W]

I don't know why, but this popped up immediately.

I have eaten
the plums
that were in
the icebox

and which
you were probably
saving
for breakfast

Forgive me
they were delicious
so sweet
and so cold

 

[Guest]

Just ask for a couple of pipes that are 1 1/4" diameter, 7" long, have them expand one end for about 1 1/2-2". Expand it just enough to slide the other pipe in. When you get home, use a hacksaw to cut some slots about 1" deep on the expanded end, then slide everything together and clamp it up. If your stock clamps are still good, use them. They take a LOT less room than a typical muffler clamp, which will hang down below the bike and get damaged by road debris.

Print out the pictures to show them what you are trying to do.

.

Are yours steel or aluminum?

 

[Guest]

Bringing this thread back to life once again. I "exhausted" all local muff/exhaust shops, no one has 1 1/4" pipe. I have ordered a length of it off of Ebay. Also no one I have talked to locally has the ability to expand the pipe so I bought a cheap Harbor Freight small pipe expander which I hope does the trick.

When this is done then the carbs will need re-synced correct?

 

[Agemax]

changing your exhaust does not require a carb synch

 

[geol]

http://www.cycleworld.com/2015/06/26/ask-kevin-why-do-my-exhaust-headers-have-crossover-tubes

Sooooo much, well BS loaded into one thread I thought I would add a bit more hehe

 

[Wingsconsin]

If the crossover is important ..
then why not build a new 'H' box of pipe 1-1/2" diameter

1 1
1-1
1 1

​

What a great illustration ... ha ha ha :topsy_turvy:

 

[Buffalo Bill]

William Carlos Williams, "so much depends"

---

so much depends
upona rusty crossover
pipe
glazed with rain
water
beside the white
chickens.
​

Lovely.
----------so much depends
on winning this debate:

I have eaten
the plums
that were in
the icebox

and which
you were probably
saving
for breakfast

Forgive me
they were delicious
so sweet
and so cold

 

[Guest]

Lovely.
----------so much depends
on winning this debate:

I have eaten
the plums
that were in
the icebox

and which
you were probably
saving
for breakfast

Forgive me
they were delicious
so sweet
and so cold

Hey, where the hell is Jeep Rusty anyway? Haven't seen him around lately.


Wing I think I would rather just slip in a couple of pipes and call it a day

 

[Cipher]

Were the crossovers used for any real power gain or just to eke out a bit lower emissions for the EPA?

 

[TxGSrider]

On a car a crossover can increase the torque, but I suspect on a twin or four even, that it lowers the sound by letting the sound waves cancel each other out some.

 

[Steve]

... I suspect on a twin or four even, that it lowers the sound by letting the sound waves cancel each other out some.

I have mentioned in another thread that when I changed a couple bikes to run without a crossover, the overall sound level did not change, just the sound. The cadence changed a bit, but it sounded just like a '79 850, instead of an '81 850. :-\\\

.