Topic: Building a Custom Exhaust: Cylinder 1-4 Orientation

[Ellz10]

Perhaps a silly question, but I need to ask nevertheless.

Bike is a 1977 Honda CB750 K

I've rebuilt it over the course of the last 2.5 years and I'm almost done. The last few things are painting the tank and rear cowl, fixing the seat, and building the exhaust.

Main reason behind building a custom exhaust is the wet sump "The Sump Thing" conversion - extended depth of the motor so the exhaust needs to be routed to either side. Even without, I always envisioned a custom exhaust on this bike.

So back on track - I'm lucky enough to have an automotive shop here in town that specializes in custom exhaust and so I went in and talked to the owner and explained the situation and he said he'd be willing to take the job. I'm doing a simple 2 into 1 (2 of them obviously) that run to the sides and straight back.

Now my question comes:  Is there any particular way the exhausts on these bikes need to be set up?
For example, does one of the two 2 into 1's need to be from cylinders 1 & 2 (just for examples sake) and the other from 3 & 4 OR does the combining of the cylinders exhaust ports have no bearing whatsoever?

[Tracksnblades1]

This is how Honda paired them on their CB750F s try wye 4 into 1…

[ekpent]

 For the sake of simplicity I would run 1 and 2 out one side and 3 and 4 out the other pretty much like having a aftermarket slip on done to a bike. I have seen headers before I think where they do the 1 and 3 and 2 and 4 out each side,  have a set of shorty 'crossovers' on a bike because they are easy to get on and off quick. Name brand will hit me later.

[Tracksnblades1]

This is what Honda did on some of their wet sumps.

Them old TT pipes may work.  You’ll know how well your carbs are synced if you use them…

[Ellz10]

This is how Honda paired them on their CB750F s try wye 4 into 1…

Interesting - so they did just do 1 & 2 into one and then 3 & 4 into the other.

For the sake of simplicity I would run 1 and 2 out one side and 3 and 4 out the other pretty much like having a aftermarket slip on done to a bike. I have seen headers before I think where they do the 1 and 3 and 2 and 4 out each side,  have a set of shorty 'crossovers' on a bike because they are easy to get on and off quick. Name brand will hit me later.

Was the purpose purely for ease of removal or is there any performance benefit I wonder?



Just to reiterate and so I'm not confusing anyone, I'm having the exhaust built and bent and welded by hand, stainless steel at the shop here in town.

I just want to make sure I'm giving them the correct information on how to go about building this exhaust.

[ekpent]

These were for sale by a member here at one time. It is a crossover design that I mentioned I have on a bike and sometimes use on new to me projects because it does not mount at the rear so easy to get on and off quickly. Note that because of a crossover its collects the 1/3 and 2/4 so for running I think its safe to go either way. More pics here of his system. Can't comment much on performance changes, maybe a little different sound character. https://www.cb750.com/threads/cb750-chrome-crossover-exhaust.430/
  Would that one clear your sump ?

[Don R]

 These were thousands of Jardine 4-2 conversions put on the stock head pipes 1-2 left and 3-4 right, they ran fine.
  The crossover method shown above 1-3 / 2-4 would likely make best use of each exhaust pulse to suck the next one out of the engine. The firing order 1-2-4-3 would make evenly timed pulses assuming proper diameter and length it could make the best power for a 4-2.
 Watch that front fender clearance too.

[spotty]

These were for sale by a member here at one time. It is a crossover design that I mentioned I have on a bike and sometimes use on new to me projects because it does not mount at the rear so easy to get on and off quickly. Note that because of a crossover its collects the 1/3 and 2/4 so for running I think its safe to go either way. More pics here of his system. Can't comment much on performance changes, maybe a little different sound character. https://www.cb750.com/threads/cb750-chrome-crossover-exhaust.430/
  Would that one clear your sump ?

i had exactly the same ones on my first 750, absolutely no baffles whatsoever, a mate told me he couldn't see my tail light at night he just followed the 2 foot long flames coming out of them, and even by my standards they were stupid loud

i doubt they'd work with the sumpthing as they run straight under the motor and were fairly close to the bottom of the motor from memory

[PeWe]

Hindle 4-2-1 for CB750 from Ripplerockracers.com
1-2, 3-4 pipes to 1
My bike work fine with that.

I have searched about 4-2-1 before and found 1-4, 2,3 setups for various engines.

[MJL]

I've got a set of pipes that run 1-4 together and 2-3 together.  Iirc one of the old race teams claimed that cylinder pairing didn't make much difference if any. Keep in mind if you do a 4-1 you'll want to have access to the oil filter.

[Ellz10]

These were for sale by a member here at one time. It is a crossover design that I mentioned I have on a bike and sometimes use on new to me projects because it does not mount at the rear so easy to get on and off quickly. Note that because of a crossover its collects the 1/3 and 2/4 so for running I think its safe to go either way. More pics here of his system. Can't comment much on performance changes, maybe a little different sound character. https://www.cb750.com/threads/cb750-chrome-crossover-exhaust.430/
  Would that one clear your sump ?

I'm not sure. I'll measure it here in a bit to see what amount of clearance I would need.

These were thousands of Jardine 4-2 conversions put on the stock head pipes 1-2 left and 3-4 right, they ran fine.
  The crossover method shown above 1-3 / 2-4 would likely make best use of each exhaust pulse to suck the next one out of the engine. The firing order 1-2-4-3 would make evenly timed pulses assuming proper diameter and length it could make the best power for a 4-2.
 Watch that front fender clearance too.

I've learned alot about the science behind exhaust systems the last couple days, I never realized how crucial exhaust systems are to the performance of a bike.

These were for sale by a member here at one time. It is a crossover design that I mentioned I have on a bike and sometimes use on new to me projects because it does not mount at the rear so easy to get on and off quickly. Note that because of a crossover its collects the 1/3 and 2/4 so for running I think its safe to go either way. More pics here of his system. Can't comment much on performance changes, maybe a little different sound character. https://www.cb750.com/threads/cb750-chrome-crossover-exhaust.430/
  Would that one clear your sump ?

i had exactly the same ones on my first 750, absolutely no baffles whatsoever, a mate told me he couldn't see my tail light at night he just followed the 2 foot long flames coming out of them, and even by my standards they were stupid loud

i doubt they'd work with the sumpthing as they run straight under the motor and were fairly close to the bottom of the motor from memory

Well that's a bummer for me then!

Hindle 4-2-1 for CB750 from Ripplerockracers.com
1-2, 3-4 pipes to 1
My bike work fine with that.

I have searched about 4-2-1 before and found 1-4, 2,3 setups for various engines.

I'm going to be doing the 2 into 1's, and there aren't any aftermarket exhaust systems on the market that don't interfere with the wet sump, unfortunately..

I've got a set of pipes that run 1-4 together and 2-3 together.  Iirc one of the old race teams claimed that cylinder pairing didn't make much difference if any. Keep in mind if you do a 4-1 you'll want to have access to the oil filter.

I wonder about that! From what I've been reading it CAN make a difference, however, how much of a difference in an application like this that isn't super modified for racing, ect I'm not entirely sure - probably not much of a difference.

[Don R]

 I have a sweet Hooker 4-2 on my brothers 750 K2 , I'll get a pic of the pairing on it. Hooker took their headers seriously. That thing was the sweetest sounding header I had, my buddy thought it sounded like an Indy car.
 2 and 3 go left, 1 and 4 go right but they are a real bag of snakes under the motor. Given the sump issue I'd just go with the Jardine style with stock head pipes. I modified that center stand to fit between a hooker headers pipes.
 The bikes next to it have Yamiya 4-4 no number pipes, and #341 repros. from cmsnl. that's a thought also.

[Ellz10]

I have a sweet Hooker 4-2 on my brothers 750 K2 , I'll get a pic of the pairing on it. Hooker took their headers seriously. That thing was the sweetest sounding header I had, my buddy thought it sounded like an Indy car.

Please do, I'd love to see how it looks!

[Stev-o]

I've got a set of pipes that run 1-4 together and 2-3 together.  Iirc one of the old race teams claimed that cylinder pairing didn't make much difference if any.

My K4 [Big Bang Bike] came to me with an aftermarket Action Fours 4 into 2 exhaust system [1&3, 2&4].
When the motor blew, I rebuilt it and installed an OEM 4 into 4 exhaust, the bike ran great with both systems installed, no difference could be felt by my butt dyno.

Here are a couple pics in the exhaust reference thread...

http://forums.sohc4.net/index.php/topic,97959.75.html

More vintage exhaust info...

http://www.hondachopper.com/garage/articles/header_guide/page4.html

What type of mufflers will you use?
Cone Engineering specializes in exhaust components, this could help them fab an awesome system for your bike...

 https://www.coneeng.com/motorcycle_components.html



 

[Don R]

 I edited my post above to show the pipes. I've owned a few of these too.
https://www.ebay.com/itm/266179712910?epid=171262117&hash=item3df98c178e:g:y44AAOSwZrJgEGw9&amdata=enc%3AAQAHAAAAwOntpSM4aZYrYjtw4d3HBTBzVyar%2F7HnX1XH%2F8N7%2B%2F11Y4Ws7XLzoAcEBbFNtuI4hAXRV85JsQCYKXoKTcKKUQjPbKOv2vC6TndG7xXKt4D4mB2TWBehRZ1JKl56GPzsfut6R3CAKzCTmCltT2qaKEPWjNAhUzmYvy%2FuzM1y0mOZLyJrmW4CRuKO23zfnr3ChmbGo%2F%2FipT032Pg%2BTdGGGbqX1Ex3kFYZiWilrsPl8kR%2BNwrlxYTHsqGgF5wPFR0Nzg%3D%3D%7Ctkp%3ABk9SR_DRnMXiYQ

[Ellz10]

Those Kooks Headers 4 into 2 look so nice. Too bad they probably wouldn't fit.

I'm honestly tempted to take my old exhaust and cut where needed and throw the torch on it and bend it away where I need to. Might be fun to see?

[Stev-o]

... throw the torch on it and bend it away where I need to.

I dont see that happening

[madmtnmotors]

I edited my post above to show the pipes. I've owned a few of these too.
https://www.ebay.com/itm/266179712910?epid=171262117&hash=item3df98c178e:g:y44AAOSwZrJgEGw9&amdata=enc%3AAQAHAAAAwOntpSM4aZYrYjtw4d3HBTBzVyar%2F7HnX1XH%2F8N7%2B%2F11Y4Ws7XLzoAcEBbFNtuI4hAXRV85JsQCYKXoKTcKKUQjPbKOv2vC6TndG7xXKt4D4mB2TWBehRZ1JKl56GPzsfut6R3CAKzCTmCltT2qaKEPWjNAhUzmYvy%2FuzM1y0mOZLyJrmW4CRuKO23zfnr3ChmbGo%2F%2FipT032Pg%2BTdGGGbqX1Ex3kFYZiWilrsPl8kR%2BNwrlxYTHsqGgF5wPFR0Nzg%3D%3D%7Ctkp%3ABk9SR_DRnMXiYQ

$900 for MAC pipes? When you can get a stainless Delkevic for $400?

https://delkevic.com/full-system-to-fit-cb750k-four-sohc-1969-1976-with-classic-straight-universal-muffler-and-stainless-steel-4-1-headers/

I know they are not 4 into 2, but hey, who's counting? 

[Stev-o]

I edited my post above to show the pipes. I've owned a few of these too.
https://www.ebay.com/itm/266179712910?epid=171262117&hash=item3df98c178e:g:y44AAOSwZrJgEGw9&amdata=enc%3AAQAHAAAAwOntpSM4aZYrYjtw4d3HBTBzVyar%2F7HnX1XH%2F8N7%2B%2F11Y4Ws7XLzoAcEBbFNtuI4hAXRV85JsQCYKXoKTcKKUQjPbKOv2vC6TndG7xXKt4D4mB2TWBehRZ1JKl56GPzsfut6R3CAKzCTmCltT2qaKEPWjNAhUzmYvy%2FuzM1y0mOZLyJrmW4CRuKO23zfnr3ChmbGo%2F%2FipT032Pg%2BTdGGGbqX1Ex3kFYZiWilrsPl8kR%2BNwrlxYTHsqGgF5wPFR0Nzg%3D%3D%7Ctkp%3ABk9SR_DRnMXiYQ

I know they are not 4 into 2, but hey, who's counting?

I think he's counting, Wilber!  Counting pipes not dollars. 
I can relate, sometimes it's more about the design than the cost.

[beemerbum]

It may be obvious but don't forget oil filter access in the design

[Tracksnblades1]

Those Kooks Headers 4 into 2 look so nice. Too bad they probably wouldn't fit.

I'm honestly tempted to take my old exhaust and cut where needed and throw the torch on it and bend it away where I need to. Might be fun to see?

Some repurposed TriClover sanitary mandrel stainless bends or ss header bends, some 304 filler rod, an inside/outside purge, and a good TIG welder, and a lot of time, you can fabricate your own professional looking  header…or  the same in 1038 and high heat paint..😇

If your around large cities, look for surplus industrial auctions sometimes it’s odd lots and leftovers. Most brand new in box or no box with scratches.  If you know a food processing plant that manufactures tomato based products (taco sauce) they will replace their piping based on the USDA’s requirements. Most of their stainless piping will be 316 with small pits ate in the inside by the tomato paste and fails the USDA inspection requiring replacement is sold for ss scrap. Still makes excellent custom exhaust systems especially if you like the satin brushed appearance.

[Ellz10]

Those Kooks Headers 4 into 2 look so nice. Too bad they probably wouldn't fit.

I'm honestly tempted to take my old exhaust and cut where needed and throw the torch on it and bend it away where I need to. Might be fun to see?

If your around large cities, look for surplus industrial auctions sometimes it’s odd lots and leftovers. Most brand new in box or no box with scratches.  If you know a food processing plant that manufactures tomato based products (taco sauce) they will replace their piping based on the USDA’s requirements. Most of their stainless piping will be 316 with small pits ate in the inside by the tomato paste and fails the USDA inspection requiring replacement is sold for ss scrap. Still makes excellent custom exhaust systems especially if you like the satin brushed appearance.

That is an insanely cool idea! The things people think of never ceases to amaze me!

It may be obvious but don't forget oil filter access in the design

Definitely at the forefront of my design process, hah!

I edited my post above to show the pipes. I've owned a few of these too.
https://www.ebay.com/itm/266179712910?epid=171262117&hash=item3df98c178e:g:y44AAOSwZrJgEGw9&amdata=enc%3AAQAHAAAAwOntpSM4aZYrYjtw4d3HBTBzVyar%2F7HnX1XH%2F8N7%2B%2F11Y4Ws7XLzoAcEBbFNtuI4hAXRV85JsQCYKXoKTcKKUQjPbKOv2vC6TndG7xXKt4D4mB2TWBehRZ1JKl56GPzsfut6R3CAKzCTmCltT2qaKEPWjNAhUzmYvy%2FuzM1y0mOZLyJrmW4CRuKO23zfnr3ChmbGo%2F%2FipT032Pg%2BTdGGGbqX1Ex3kFYZiWilrsPl8kR%2BNwrlxYTHsqGgF5wPFR0Nzg%3D%3D%7Ctkp%3ABk9SR_DRnMXiYQ

$900 for MAC pipes? When you can get a stainless Delkevic for $400?

https://delkevic.com/full-system-to-fit-cb750k-four-sohc-1969-1976-with-classic-straight-universal-muffler-and-stainless-steel-4-1-headers/

I know they are not 4 into 2, but hey, who's counting? 

You have no idea yow badly I wish I could just go this route and call it done! Unfortunately that wet sump conversion throws a huge monkey wrench into the equation and force me to deviate from such ideas!

I edited my post above to show the pipes. I've owned a few of these too.
https://www.ebay.com/itm/266179712910?epid=171262117&hash=item3df98c178e:g:y44AAOSwZrJgEGw9&amdata=enc%3AAQAHAAAAwOntpSM4aZYrYjtw4d3HBTBzVyar%2F7HnX1XH%2F8N7%2B%2F11Y4Ws7XLzoAcEBbFNtuI4hAXRV85JsQCYKXoKTcKKUQjPbKOv2vC6TndG7xXKt4D4mB2TWBehRZ1JKl56GPzsfut6R3CAKzCTmCltT2qaKEPWjNAhUzmYvy%2FuzM1y0mOZLyJrmW4CRuKO23zfnr3ChmbGo%2F%2FipT032Pg%2BTdGGGbqX1Ex3kFYZiWilrsPl8kR%2BNwrlxYTHsqGgF5wPFR0Nzg%3D%3D%7Ctkp%3ABk9SR_DRnMXiYQ

I know they are not 4 into 2, but hey, who's counting?

I can relate, sometimes it's more about the design than the cost.

Not often for me, but in this case, yes.

[Tracksnblades1]

Ellz10,

Don’t forget to check out the cb750/900 dohc header lead pipes (primaries). They are wet sump engines. I’ve never tried them but have been told the dohc is a taller engine and when using their header on a sohc 750 they hang down quite a bit lower. If true it would save having to fabricate the primaries. The

Check with the Captain or his buddy Kmb69 on here that’s building his own billet crankshafts, billet big valve, big port cylinder head, roller tip rockers, and gear driven primaries. They both have dohc experience and will know if they’re a direct bolt up to the sohc cylinder head.

Captain has big HP dohcs with gear driven primaries, both of them are on a completely different level…😁🎯

[Don R]

 I have run the same cb900 Vance and Hines 4-1 header on both a cb900 and a K2 cb750. It took a little encouraging to bolt it on but it went. Just due to the 4-1 design and the angled ports.

[Ellz10]

Ellz10,

Don’t forget to check out the cb750/900 dohc header lead pipes (primaries). They are wet sump engines. I’ve never tried them but have been told the dohc is a taller engine and when using their header on a sohc 750 they hang down quite a bit lower. If true it would save having to fabricate the primaries. The

Check with the Captain or his buddy Kmb69 on here that’s building his own billet crankshafts, billet big valve, big port cylinder head, roller tip rockers, and gear driven primaries. They both have dohc experience and will know if they’re a direct bolt up to the sohc cylinder head.

Captain has big HP dohcs with gear driven primaries, both of them are on a completely different level…😁🎯

That's a great idea!!! I never thought of that! I went ahead and messaged Kmb69 after I read this, so I'll wait to see what he has to say!

If that's true, it would save me alot of time and perhaps even some money if I were able to purchase the header itself then I could fabricate my own pipes from there (possibly).

I have run the same cb900 Vance and Hines 4-1 header on both a cb900 and a K2 cb750. It took a little encouraging to bolt it on but it went. Just due to the 4-1 design and the angled ports.

Successfully and without any exhaust leaks???