Author Topic: CB750F 4 into 1 exhaust - " header to muffler " diameter please  (Read 4153 times)

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Offline IndianRider

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hey all ..

i have a 1978 CB 750 K bike and the stock 4 into 4 exhausts have the baffles rattling and some small rusted holes which i taped up with an exhaust tape..

i just won a bid on '78 CB 750 F  series stock 4 into 1 header and was wondering what the diameter of the collectotor outlet is .. Im planning to install a cheap slip on muffler .. i like the look of the kerker slip on mufflers that fit most of the the kawasaki bikes in the 80's ..  the straight cylindrical mufflers with the aluminum look and are are about 12-16 inches in length .. wish a pic could help here ..

1: does the stock CB 750F muffler slip on OVER the header outlet or viceversa ? what is the exact diameter (inner and outer) at the outlet ..

2: was the stock 750F muffler 1 peice or was there a small mid pipe ? i wonder if i would need a mid pipe to

3: i know there is a Mac muffler available for about $110 on ebay that slips on the stock F header but does the Mac have a baffle ?

4: there was someone on here with a Jardine slip on muffler fitted to a stock cb750F 4-1 header but i cannot find he post ..

thanks all ..  :D
« Last Edit: April 23, 2007, 02:21:20 PM by IndianRider »



Offline mick750F

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #1 on: April 23, 2007, 07:45:42 PM »
1. The muffler slips over the collector but there is a gasket material between the two. I'll check the collector in my shop tomorrow for the diameter if it hasn't been answered already.

2. One long muffler and it's heavy. I dissected mine after it rotted out. There are multiple baffles, three I think, and packing material.

3. The POS MAC muffler on my bike has two baffles and no packing material. It's not a slip-on though...it's part of a complete system. Your intended muffler may differ. Can you tell I'm not real impressed with the MAC?  ;) It's loud for my taste...I liked the stock sound but couldn't find a decent muffler when I needed one. Also, I'm also not impressed with MAC quality. It was a wrestling match to install and the head pipes have started to rust after a couple of years. The one upside I see in the MAC is that it's much lighter than the stock system.

4. Can't help you on that...

Mike
'78 CB750F 
 http://gallery.sohc4.net/members/personal/mick750F
Glosta, MA
It's not the heat...it's the humanity.



jdigga

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #2 on: April 23, 2007, 08:03:23 PM »
I just got a 4-1 header off eBay a couple weeks ago.  The collector OD is 2-1/8".  I've been searching for a 2-1/4" ID muffler but they seem scarce.



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #3 on: April 23, 2007, 09:01:22 PM »
thanks for the replies and good info ..

ive been searching for a 2 1/4 inch inner diameter muffler as well and you are right they are scarce .. i was at advance auto parts the other day and noticed these exhasut pipe adapters which are available in various combinations of inlet and outlet diameters for about $4) ..  so that might be an option to try to fit a muffler on the stock headers ..

another option i was thinking about was to install that softer band/ring type of gasket that goes inbetween the header and muffler if the muffler inner diameter is too big and clamp it real tight  ..  i was trying to figure out where to buy the soft gasket material on the web and cannot find it .. my 2001 kawasaki ninja had that gasket material that mick750F was talking about ..if i remember, it was a pretty thick (1/8 to 1/4 inch) material that sealed real well between the header and muffler ..   

i wouldnt want a loud MAC muffler ..  something like a stock muffler from the 90's sport bikes would be nice for a  quiet but deep sound ..

jdigga, please update this thread if you find a 2 1/4 inch inner diameter muffler and i will do the same ..  thanks ..

« Last Edit: April 23, 2007, 09:04:41 PM by IndianRider »



Offline merc2dogs

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #4 on: April 23, 2007, 09:26:12 PM »
I have a mac, and a stock 4:1 pipe both have a 2.5 inch od collector.

 A local muffler supply company (not a regular muffler shop) carries stainless tips, highly polished that fit perfectly on the collectors. $29. for a 22 inch x 4" slash cut tip.  have them available in several lengths and diameters. also carry resonators/glass packs that work very well slipped inside of them.

Ken.

 



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #5 on: April 23, 2007, 09:44:41 PM »
so the "inner" diameter (ID) of the '78 cb750F stock header outlet is 2 1/8 inch and the "outer" diameter (OD) is 2 1/2 inch .. is this correct ..   

merc2dogs .. any addiitonal info on the muffler supply store ?  thanks .. 



jdigga

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #6 on: April 23, 2007, 10:00:04 PM »
Hmm...

I was thinking "ID" as "inlet diameter" and "OD" as "outlet diameter".

It seems like a lot of space to make up between 2-1/8" and 2-1/2".  We must be talking about different things.

Well here's a pic of what I got.  I guess it's technically a 4-2-1.  I'm not even sure now what year it's supposed to be from.

IndianRider, is it the same as what you got?  Because I saw another one on eBay recently.  Or is your collector part stacked square instead of flat?



« Last Edit: April 23, 2007, 10:05:27 PM by jdigga »



Offline rocky

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #7 on: April 23, 2007, 10:47:04 PM »
I have a used 1978 cb750f muffler. It is dented on the bottom and does not really show on the bike. It is in good solid condition otherwise.Can send pictures if interested.



Offline mick750F

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #8 on: April 23, 2007, 11:05:55 PM »
so the "inner" diameter (ID) of the '78 cb750F stock header outlet is 2 1/8 inch and the "outer" diameter (OD) is 2 1/2 inch .. is this correct ..   

merc2dogs .. any addiitonal info on the muffler supply store ?  thanks .. 

  The 2-1/8" diameter sounds right for the OD of the stock collector but I'll check it tomorrow. 2-1/2" sounds right for the OD of the MAC collector which I might be able to check tomorrow.

   The gasket is/was available from Honda...part #18391-390-000 or #18391-390-405

Mike
'78 CB750F 
 http://gallery.sohc4.net/members/personal/mick750F
Glosta, MA
It's not the heat...it's the humanity.



Offline merc2dogs

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #9 on: April 23, 2007, 11:23:45 PM »
that pipes the same, but the collector's different than the one I have, Mine are both 2.5 outside.

 Can't find the actual tips I'm talking about, but here are some similar, but different brand

http://www.amazon.com/b?ie=UTF8&node=13675641&me=A1MK3HAFHEKCQU

I'll stop by in the afternoon and check what brand and sizes they have available at the local shop.
 
I spent some time there the other day checking out mufflers and tips, but was looking for 2.5

can't remember the brand name on them right off, but know it was a familiar name brand.

 seems like that's a double wall AND metric pipe (2 1/8 is ~60mm isn't it?)

 If so, you -may- be stuck using a factory muffler, or a reducing sleeve inside the muffler.

 If you have a well equipped muffler shop nearby, they should be able to neck down a section of pipe for you to use as a reducer.

 Home built is easily done with a strip of steel wrapped around then slash or  'V' cut the ends so they butt smoothly together thickness to fit.

 You have that shoulder on the collector so you should be able to butt the muffler up against it to keep a clean look. 

  Also, the 4 into 2 into 1 is generally called a tri-Y, made famous mostly by Shelby in the mustangs
 
  Has me wondering now, I'm working on a deal to get an F with a bad muffler, was expecting to be able to use the same arrangement I have on the two other bikes, may have to change plans!

Ken.
 
 



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #10 on: April 24, 2007, 07:32:14 AM »
I have a used 1978 cb750f muffler. It is dented on the bottom and does not really show on the bike. It is in good solid condition otherwise.Can send pictures if interested.

sure .. id be intered in some pics .. thanks ..



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #11 on: April 24, 2007, 07:42:26 AM »
Hmm...

I was thinking "ID" as "inlet diameter" and "OD" as "outlet diameter".

It seems like a lot of space to make up between 2-1/8" and 2-1/2". We must be talking about different things.

Well here's a pic of what I got. I guess it's technically a 4-2-1. I'm not even sure now what year it's supposed to be from.

IndianRider, is it the same as what you got? Because I saw another one on eBay recently. Or is your collector part stacked square instead of flat?






here u go jdigga .. i won these on ebay and they havent been delivered yet .. looks like the collector outlet is slightly different on my headers (1978-F3) .. my collector outlet seems to have a step but yours outlet seem to be straight  .. arent the F0 & F1 headers slightly different than the F2 and f3 headers ?








Offline adams77

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #12 on: April 24, 2007, 07:52:30 AM »
I had the same problem finding a muffler that works 'til now.  Its a $25 cherry bomb.

« Last Edit: April 24, 2007, 07:54:19 AM by adams77 »



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #13 on: April 24, 2007, 08:01:23 AM »
the cherry bomb looks good for the price.. did you have to use the soft gasket amterial or did it fit right in ? would you have a sound file and tell us where you can get it .. i think they sell the cherry bomb automotiove exhausts at pep boys dont they ? 



jdigga

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #14 on: April 24, 2007, 08:22:08 AM »
IndianRider: Actually, I think yours is the same as mine except yours still has the muffler sleeve attached to the collector (what you said appears to be a step).  There was yet another one of these headers being parted out on eBay and I remember that piece.

Yeah, I'm liking that Cherry Bomb too.



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #15 on: April 24, 2007, 08:47:09 AM »


here is the 1978 CB 750 F parts diagram ..  looks like the "step" on my collector is part # 13 on the diagram ..

i need to visit the muffler shop and find out if they fabricate a midpipe so the headers can accept a mordern sport bike muffler which is slightly upswept .. since ive already repalced the from spoked wheel on my K8 with a comstar for dual disc purposes (hopefully i can find a rear drum comstar), an upswept muffler design might not look that bad .. 




Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #16 on: April 24, 2007, 08:50:36 AM »
a couple of pics of my K8 .. check out the tape repairs made to stock exhausts .. there are small holes (1/4 inch) on 3 of the 4 exhausts ..and the mufflers rattle a bit when i shake the mufflers, hence the need for a 4 into 1 replacement ..









Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #17 on: April 24, 2007, 08:52:36 AM »
this how the exhausts looked when i got the bike ..



 



jdigga

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #18 on: April 24, 2007, 08:58:53 AM »
Mmm, dual discs... *drool*

I was looking at Jegs and they have cherry bombs with angled inlets/outlets.

http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_769804_-1_10265

For me I'm just trying to piece together a cheap alternative to my 4-2 turnouts.  If I had the money and the motivation, I'd splurge for a new Kerker setup from Dynoman.



Offline adams77

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #19 on: April 24, 2007, 09:41:32 AM »
the cherry bomb looks good for the price.. did you have to use the soft gasket amterial or did it fit right in ? would you have a sound file and tell us where you can get it .. i think they sell the cherry bomb automotiove exhausts at pep boys dont they ? 


I had to cut some slots to allow the muffler flange to close together.  It sounds great to me, but I like an aggressive tone.  It only takes some of the high pitch out of the exhaust note.  You should be able to pick up a thrush cherry bomb at any auto parts store.  I even saw some of the "old style" on ebay for a few hundred dollars.



Offline mick750F

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #20 on: April 24, 2007, 10:35:25 AM »


here is the 1978 CB 750 F parts diagram ..  looks like the "step" on my collector is part # 13 on the diagram ..

i need to visit the muffler shop and find out if they fabricate a midpipe so the headers can accept a mordern sport bike muffler which is slightly upswept .. since ive already repalced the from spoked wheel on my K8 with a comstar for dual disc purposes (hopefully i can find a rear drum comstar), an upswept muffler design might not look that bad .. 




   Part #13 is the gasket I mentioned earlier. It slips over the collector then the muffler slips over it. It would seem to be some type of composite...metal/asbestos perhaps?

   I checked the stock collector I have. The outlet has a 2-1/8" OD and a 2" ID.

Mike
'78 CB750F 
 http://gallery.sohc4.net/members/personal/mick750F
Glosta, MA
It's not the heat...it's the humanity.



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #21 on: April 28, 2007, 07:48:45 PM »
check out the pics of the cb750f stock 4 into 1 header on my k8 .. boy it sounds mean without a muffler  ... i measured the collector outlet "outer" diameter and it is 2 1/8 inches .. just need to find a decent slip on muffler for it .. heres a pic ..




« Last Edit: April 28, 2007, 10:49:39 PM by IndianRider »



Offline adams77

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #22 on: April 28, 2007, 08:23:20 PM »
I found a slip on exhaust tip (no muffler) at pep boys for $10.  I like the roar better, I will be selling the cherry bomb from the earlier post.




Offline merc2dogs

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #23 on: April 28, 2007, 08:49:35 PM »

 I for one find this odd.

 I have my bike, with the MAC on it, and it has a 2-1/2 inch OD collector, the  76 hondamatic has the same size collector on the stock pipes as the MAC, when I first got it running I used the mac can on it for test runs etc.
 just pushed a 76 F home this morning for parts, checked the exhaust out pulled the muffler for the auto, and it will work right

  Mac pipe -will- work on the F pipe, but instead of the thick pad you'd need a few wraps of aluminum muffler tape or similar, pipe fits on, but has some rock to it. feels like about a 16'th clearance, which should be burned up with three wraps of 'muffler mend'

 Doesn't make sense why honda would bother making two otherwise identical mufflers with such a minute difference in OD

 Ken.



Offline IndianRider

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Re: CB750F 4 into 1 exhaust - " header to muffler " diameter please
« Reply #24 on: April 30, 2007, 07:53:46 AM »
dang .. this would have been a nice muffler to slip on .. its for a KZ 550 and sold for $75 on ebay  .. it had a 2 inch inner diameter .. an exhaust adaptor would have allowed this one to fit the headers ..


 

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