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Author Topic: Custom crossover dual exhaust question - CB750  (Read 2943 times)

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Offline Mr Freeze

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Custom crossover dual exhaust question - CB750
« on: February 09, 2016, 02:19:08 PM »
So I am going to start the process of designing a custom dual exhaust setup from stainless steel for a 1978 K motor. Obviously there are plenty of choices for dual exhausts that couple cylinders 1-2 & 3-4, but I have not seen really one that is a crossover 1-4 & 2-3 set of pipes. Is there anyone here that can chime in as to what the advantages would be in doing so versus a typical 1-2 / 3-4 dual exhaust?
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Offline BobbyR

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Re: Custom crossover dual exhaust question - CB750
« Reply #1 on: February 09, 2016, 02:32:12 PM »
Your biggest concern will be a change in backpressure. Sounds like a great project. Post pics. 
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Offline Terry in Australia

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Re: Custom crossover dual exhaust question - CB750
« Reply #2 on: February 09, 2016, 03:20:09 PM »
I've got a set of Peter Allen (not the singer) crossover 4 into 2 race pipes from the 1970's, they really gave my bike a lift, I took them off when I scored a genuine Yoshi 4 into 1 which wasn't any improvement over the 4 into 2.

The Yoshi's gone now, so I think I'll put the 4 into 2 back on again. Advantages? Equal length primaries, better low end torque, better sound, and I forget the rest, ha ha! Cheers, Terry. ,D
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Offline mystic_1

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Re: Custom crossover dual exhaust question - CB750
« Reply #3 on: February 09, 2016, 04:37:52 PM »
The firing order is 1-2-4-3, so with a "typical" 4-2 that combines 1+2 on the left and 3+4 on the right, you're getting pulses in this order: Left, Left, Right, Right.

With a 4-2 that combines 1+4 and then 2+3, you'll get pulses like this: Left, Right, Left, Right.

In the first scenario, the left side muffler sees two quick pulses and then nothing for two more cycles.  Same on the right.

In the second scenario, each muffler sees evenly spaced pulses and pauses.

Does any of this matter?  I have no idea  ;D

mystic_1
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Offline seanbarney41

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Re: Custom crossover dual exhaust question - CB750
« Reply #4 on: February 09, 2016, 05:12:18 PM »
...gives it that oh so awsome and bubbly aircooled VW sound...like this
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Offline Mr Freeze

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Re: Custom crossover dual exhaust question - CB750
« Reply #5 on: February 09, 2016, 07:07:23 PM »
Quote from: Terry in Australia on February 09, 2016, 03:20:09 PM
I've got a set of Peter Allen (not the singer) crossover 4 into 2 race pipes from the 1970's, they really gave my bike a lift, I took them off when I scored a genuine Yoshi 4 into 1 which wasn't any improvement over the 4 into 2.

The Yoshi's gone now, so I think I'll put the 4 into 2 back on again. Advantages? Equal length primaries, better low end torque, better sound, and I forget the rest, ha ha! Cheers, Terry. ,D

Terry do you have any pictures of those Peter allen pipes?! I'm looking for inspiration on the front section where it will crossover.

I am aware that the back pressure will change, but this isnt going on a stock motor either. I have a set of short mufflers with baffles that I plan to run with the pipes. Either way it should be a cool project.
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Offline Terry in Australia

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Re: Custom crossover dual exhaust question - CB750
« Reply #6 on: February 09, 2016, 07:59:11 PM »
I do mate, I'll interrogate my photobucket account when I get back to my apartment and post a pic. Cheers, Terry. ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline evanphi

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Re: Custom crossover dual exhaust question - CB750
« Reply #7 on: February 10, 2016, 05:18:21 AM »
Looking forward to pics... and sound clips!
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Offline Mr Freeze

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Re: Custom crossover dual exhaust question - CB750
« Reply #8 on: February 10, 2016, 07:37:53 AM »
Quote from: evanphi on February 10, 2016, 05:18:21 AM
Looking forward to pics... and sound clips!

Gonna be a while until we get there haha. I have a whole engine build to do as well.
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Offline Terry in Australia

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Re: Custom crossover dual exhaust question - CB750
« Reply #9 on: February 10, 2016, 12:07:08 PM »
Bugger, I forgot to post a pic, I'll do it tonight. ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline Terry in Australia

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Re: Custom crossover dual exhaust question - CB750
« Reply #10 on: February 13, 2016, 03:04:01 AM »
Well I must apologise to the OP, I forgot to post the pic of my bike with the custom crossover system but I just remembered now, so here it is. Cheers, Terry. ;D

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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline cougar

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Re: Custom crossover dual exhaust question - CB750
« Reply #11 on: February 13, 2016, 10:25:44 AM »
Mr. Freeze ; While the link I'm providing isn't specifically for 4>2 exhaust, it may give you some insight as to the performance of different designs. Hope it helps.   http://www.hondachopper.com/garage/articles/exhaust_testing/page1.html   Oh btw the link is to the first page of the 4 page article :) !!   ...cougar...
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Offline Mr Freeze

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Re: Custom crossover dual exhaust question - CB750
« Reply #12 on: February 13, 2016, 02:07:23 PM »
PM'ed you Terry.
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