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CL350 mufflers

Knoxes

Veteran Member
Joined
Jun 22, 2020
Total Posts
257
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Location
Chapel Hill NC
Just trying to add some content to the new website.

My 71 CL350 mufflers are rusting out in a couple of different spots. I was able to weld a 1x2" patch to cover one, but I expect that this will continue to be a problem. I already noticed that another spot blew out after I patched the first one. And they're getting quite loud, which I don't like at all. My target is a stock sound and look.

The aftermarket for these is almost non-existent. I found one option on CMC, but it looks like they would require some modifications to use the stock heat shield. One reviewer noted that they are louder than stock. I can't find anything that is actually a bolt on/weld on with the stock cover or brackets. Looking for the best alternative if anyone has one.

Secondly, I've found some mention of opening them up and rebuilding the internals, but no details on that. Does anyone have any experience or ideas about that as an option?
 
They are a completely welded unit so to open one up will require cutting the weld off, not going to leave much material to reweld.
If I was going about a repair of them I would be making a patch section that would cover all of the holes current and future by making it start at the weld seam and wrap up the muffler at least 1/2" beyond the rot. If it's on the outer seaction then have the top of the patch hidden behind the heat shield. Also I would try to have the patch piece extend from front to rear.
 
I had this setup for a while - Emgo shorty mufflers. I had to mod them a bit to fit right and to be clamp-able, and fab a new mounting bracket for the rear, but they looked pretty good. Problem was, they were LOUD, and repacking the mufflers with better material didn’t really help.

7EEB842E-E21E-47EA-948A-D9E3D556D9A6.jpeg
 
I really don't understand why the only semi-"replacement" mufflers that seem to be available these days are all reported to be so loud. Is making a quiet muffler a lot harder to make? Is it harder to do so and retain a kind of "universal" fitment due to differences in required back pressures? (Not that I claim to know what I'm talking about.)

I'm assuming I'm going to need to figure out replacements sooner rather than later and I really don't want to be riding an obnoxious bike thorough the neighborhood...
 
Which is why I idle/low rev my straight-piped 450 out of my neighborhood every time I ride it, which isn't much during the summer and I'm sure the neighbors are happy about that
 
I really don't understand why the only semi-"replacement" mufflers that seem to be available these days are all reported to be so loud. Is making a quiet muffler a lot harder to make? Is it harder to do so and retain a kind of "universal" fitment due to differences in required back pressures? (Not that I claim to know what I'm talking about.)

I'm assuming I'm going to need to figure out replacements sooner rather than later and I really don't want to be riding an obnoxious bike thorough the neighborhood...

I used to have a pair of Bates shorty mufflers that looked similar in size and shape to the Emgos, but were much more quiet. They had a fixed front baffle and a removable rear one, but weren’t straight-through like the Emgos are. Too bad those aren’t around any more...
 
Just to commit to closing out threads, or at least updating the information, I've spent hours searching for a decent stock sound/style and can't find anything. CMC's look like the best option, but I'm not sold on them yet.

I'm still mulling over cutting off the frame side of the stamped upper muffler just to see what it looks like inside and if there is any chance of rebuilding what's in there. In spite of my very limited welding skills, I was able to weld the patch on without any problem. So, worse case scenario, I have to turn it over to a pro to weld it back together. I probably won't do that until I've at least committed to an after market pair of mufflers as a backup.
 
Any ideas about the volume on those vs the stock mufflers?

I’d ask around here and see if anyone has those, either on CL or CB headers. Maybe they can give some indication of how loud they are. Of course, loudness can be subjective. I’d want to know what sort of baffling is in them.
 
I'm still mulling over cutting off the frame side of the stamped upper muffler just to see what it looks like inside and if there is any chance of rebuilding what's in there.

Following in case this becomes a reality. I’m uber curious about this, not having found any real acceptable alternatives imo.


Ed
1972 Honda CL350
 
Very late on my follow up, but I wanted to make sure I didn't leave anyone hanging in regard to how the EMGO 80-25300Bs turned out.

I'm using aftermarket headers, so make sure you double check your fitment before ordering. Dry fitting them indicated that the uppermost header needed to be bent in order to allow enough clearance between 1) the rear spring and muffler, and, 2) the mufflers themselves.

Having a friend with a work shop helps, especially when that shop includes a welding jig table. We jigged up the pipe and bent it manually, taking our time to ensure none of the welds became stressed. All told, the pipe was bent about two inches out and an inch up.

mufflers-01.jpg

Each muffler came with a mounting bracket. Another dry fit followed by some quick and dirty fabrication gives us a decent mounting bracket:

mufflers-02.jpgmufflers-03.jpgmufflers-04.jpgmufflers-05.jpgmufflers-06.jpgmufflers-07.jpg

Final product!

mufflers-08.jpgmufflers-09.jpg

I was thinking about wrapping the headers but eventually came to the conclusion that the raw headers with black mufflers look pretty rad given the color flow of the engine and the powder coating; I'm just going to leave things as they are for now. :)
 
I think they'd look great ceramic coated too. Good job getting them hung and aligned properly
 
Looks great, I like that raw look too. I'm guessing you can just paint them with a high temp clear(?)

I'm sure I could but I like the way they look right now; check out my new thread in Projects and Builds for a more complete look. Just need to get my air box covers put back on, but I'm waiting on, hopefully, the last parts order I make in a long time. :)

Also, your earlier comment about generic loudness? Yeah, these things are much louder than I expected. At idle it sounds like a normal, happy bike... start riding and rev it up a bit? Jesús Cristo! I think I'm going to have to creep out of the neighborhood doing about 10 mph before I feel comfortable letting it rip. Maybe I'm taking crazy pills, but part of me feel likes this little 350 is louder than my Harley. lol
 
I know it's difficult to match how quiet the OEM Honda CL mufflers are.I was considering(if I ever had a shop to make my own and if I was to purchase a CL someday)to possibly take both old mufflers and cut the seams all the way around,then commit to make a pair of custom made repros to the same specifications as the OEM CL mufflers:A Big job.I don't know how to weld so that would require me to enlist someone who is good at welding thin steel(even stainless steel if desired ??)and take my time and enjoy the finished project once complete.I'm sure Everyone's ears would appreciate my bike with less noise pollution.I remember someone on the HT forum had done this a few years back:a big project,but not insurmountable by any means.The other thing would be what coating to choose for lasting good looks.I can't afford chrome,but sure enjoy it. :)

My 1st motorcycle(I was 17) was a 1966' Honda CL77 305.I bought it from a guy who must have removed the separate inner baffles from each pipe And the outer 2 into 1 OEM muffler which really left the bike extremely loud.My mother always complained.. I eventually purchased all new baffles and the muffler:it sounded great and was running excellent.
 
I know it's difficult to match how quiet the OEM Honda CL mufflers are.I was considering(if I ever had a shop to make my own and if I was to purchase a CL someday)to possibly take both old mufflers and cut the seams all the way around,then commit to make a pair of custom made repros to the same specifications as the OEM CL mufflers:A Big job.I don't know how to weld so that would require me to enlist someone who is good at welding thin steel(even stainless steel if desired ??)and take my time and enjoy the finished project once complete.I'm sure Everyone's ears would appreciate my bike with less noise pollution.I remember someone on the HT forum had done this a few years back:a big project,but not insurmountable by any means.The other thing would be what coating to choose for lasting good looks.I can't afford chrome,but sure enjoy it. :)

My 1st motorcycle(I was 17) was a 1966' Honda CL77 305.I bought it from a guy who must have removed the separate inner baffles from each pipe And the outer 2 into 1 OEM muffler which really left the bike extremely loud.My mother always complained.. I eventually purchased all new baffles and the muffler:it sounded great and was running excellent.

Over this last summer I found a guy in my area who was trying to get the heck out of Minneapolis because the recent riots were, literally, in his backyard. He sold me his entire excess stock of 70s Honda parts for a very reasonable amount. So I'm currently sitting on a spare engine, about three sets of carbs, and a pair of CL-style headers and mufflers. I was planning on getting a MIG welder in the next six months so I can do some custom fabrication for a few projects I have in the hopper. The idea of cracking open the mufflers sitting in my garage has most certainly crossed my mind. Worst case scenario, I take a bunch of measurements and pictures and then slap it up on this forum so some other sucker can make them. :)
 
Was there a conclusion to what may be a good after market muffler replacement for the CL350 but not be loud, look era correct and not impossible to install?
 
Was there a conclusion to what may be a good after market muffler replacement for the CL350 but not be loud, look era correct and not impossible to install?

To add to this, will the later cl350 exhaust headers work on the 1968-69 CL350? From what I can tell, they have a different part number so I would think maybe not. I know the muffler is different, I am just looking at the header pipes right now.
 
I don't believe there is any significant difference in CL350s along the way that would affect the header pipes from any year or K-series fitting another other than possibly the mounting brackets
 
Sort of related question - does anyone know if the heat shields change over the years or would upper and lower heat shields work for all K0-K5 on the CL350s? Thanks
 
The forward one, maybe. The rear ones definitely not between the 68/69 and 70's as the early one is a single one and the later one are separate for each muffler.
 
The forward one, maybe. The rear ones definitely not between the 68/69 and 70's as the early one is a single one and the later one are separate for each muffler.

So if I have 73 and we are talking rear shields, then they should work if they are lower and upper separate right?
 
I am not sure. I know the 1970 to the last one (1974?) Have the separate rear shields. The 1970 had the muffler attached to the head pipe on one and seperate on the other. 1971 and up were seperate on both. Therefore, 1970 and the later may not exchange. I can look at parts diagrams later tomorrow and get a better idea.
 
Screen Shot 2020-12-20 at 9.09.34 AM.jpg

Is it reasonable to clamp on stock muffler to aftermarket pipe? Its almost the reverse of what many have done in the past which was cut off original OEM mufflers and put on aftermarket shorty's, right? How would one know if its possible to put on OEM muffler to newer pipe?
 
Given the proper fit for the muffler at the clamping point, I see no reason why you couldn't. Seems odd for the header pipe to be the part that went bad though, had to be an unusual situation
 
I really don't understand why the only semi-"replacement" mufflers that seem to be available these days are all reported to be so loud. Is making a quiet muffler a lot harder to make? Is it harder to do so and retain a kind of "universal" fitment due to differences in required back pressures? (Not that I claim to know what I'm talking about.)

I'm assuming I'm going to need to figure out replacements sooner rather than later and I really don't want to be riding an obnoxious bike thorough the neighborhood...

Cone Engineering makes a quiet core muffler that would work well for the CL350. I built a header to resemble the old Hooker 2-1 and used a Cone Engineering 18" Quite Core muffler. They are expensive though at $160 ish a piece, + shipping. It does look good though. I've seen others build the 2-1 at the end of the stock headers as well and use a single muffler as well. For me, I love the sound of the 2-1 twin vs stock 2-2.

My bike with the Cone Engineering Muffler

Untitled by Jeremy Hedrick, on Flickr

The sound




 
Maybe not with the depth of loudness the Harley has, but they can be loud with straight pipes. Listen to my 450


with wide open pipes or the VW Beetle tips mine started giving me Tinnitus even with ear plugs in. I finally decided my hearing was more important. I'm sure the Harley potato hurts riders hearing as well over the years but there is a high pitched buzz developed on these bikes with wide open pipes that kills my ears over 6,000 rpms.
 
Cone Engineering makes a quiet core muffler that would work well for the CL350. I built a header to resemble the old Hooker 2-1 and used a Cone Engineering 18" Quite Core muffler. They are expensive though at $160 ish a piece, + shipping. It does look good though. I've seen others build the 2-1 at the end of the stock headers as well and use a single muffler as well. For me, I love the sound of the 2-1 twin vs stock 2-2.

My bike with the Cone Engineering Muffler

Untitled by Jeremy Hedrick, on Flickr

The sound





One more option on muffler is a Harley Muffler. This one is from a early 00 Dyna I believe. Same bike, just different muffler.

Untitled by Jeremy Hedrick, on Flickr
 
with wide open pipes or the VW Beetle tips mine started giving me Tinnitus even with ear plugs in. I finally decided my hearing was more important. I'm sure the Harley potato hurts riders hearing as well over the years but there is a high pitched buzz developed on these bikes with wide open pipes that kills my ears over 6,000 rpms.

Coming from an older generation that didn't think about it much except after a louder-than-usual concert, I've had a bit of tinnitus for a couple decades now. I wear good ear plugs when I ride it to avoid making things any worse and I'm not experiencing any change, but we're all different in our tolerance levels. I can still hear the quietest of sounds easily, even more than my wife who has been to far fewer concerts and spent zero time around loud tools or engines, so I consider myself lucky at this point. And, I don't ride every day either so that limits the exposure.
 
First of all your bike is completely awesome in a different way. You should try and get your bike picked-up by Hollywood to put in a movie! It's still very vintage but uniquely modernish!

Great suggestion on going to this mulfler and I will look into. I am not a purist for OEM - I like both ways. I also don't mind a little loud than stock but my current situation is so loud its rattling my brain. There is one main problem to your reply around 2 words . . . "I built". I am so new to this, it's a good day if I can unscrew something without stripping it out. Building and engineering something like yours seems far stretching for my abilities. You don't happen to have a youtube video of this project do you?
 
First of all your bike is completely awesome in a different way. You should try and get your bike picked-up by Hollywood to put in a movie! It's still very vintage but uniquely modernish!

Great suggestion on going to this mulfler and I will look into. I am not a purist for OEM - I like both ways. I also don't mind a little loud than stock but my current situation is so loud its rattling my brain. There is one main problem to your reply around 2 words . . . "I built". I am so new to this, it's a good day if I can unscrew something without stripping it out. Building and engineering something like yours seems far stretching for my abilities. You don't happen to have a youtube video of this project do you?

Haha! Thanks for the great compliment. Its gone through a few variations through the build. I have a new diamond stitch seat cover made of real leather that I am working on.

As far as the single muffler option you could use a Yonaka merger at the end of your headers and use a 1.75 ID muffler ( Cone and Harley, go to a motorcycle junkyard, has these)

https://www.yonaka.com/2_1_Merge_Collector_1_5_to_1_75_p/ymecmc15175.htm

This bike on DotheTon would be a good example with the merger at the end of the headers. These engines perform best with the muffler at least to the rear axle and even extending past a bit.

https://www.dotheton.com/index.php?threads/1972-cb175-2-1-exhaust-build.47394/
 
Haha! Thanks for the great compliment. Its gone through a few variations through the build. I have a new diamond stitch seat cover made of real leather that I am working on.

As far as the single muffler option you could use a Yonaka merger at the end of your headers and use a 1.75 ID muffler ( Cone and Harley, go to a motorcycle junkyard, has these)

https://www.yonaka.com/2_1_Merge_Collector_1_5_to_1_75_p/ymecmc15175.htm

This bike on DotheTon would be a good example with the merger at the end of the headers. These engines perform best with the muffler at least to the rear axle and even extending past a bit.

https://www.dotheton.com/index.php?threads/1972-cb175-2-1-exhaust-build.47394/


Thanks . . . I see you're a mountain biker too! Road trip - come out east and race bikes/ride our trails for a week and HELP me:) Mtbx and CX are my main hobbies. I am trying to branch out with vintage motorcycles, but now I see the need to be more of a mechanic than anything is req'd to do this!
 
Follow-up questions:

Is an OEM header pipe for CL350 "special" or not? It has been mentioned that the OEM Honda exhaust system is less loud and Honda really knew how to design the exhaust just right for flow/performance. I believe its well established aftermarkets are louder consistently and performance not always the best. Is that engineering and performance ALL in the silencer/muffler or the entire length of pipe and silencer? ie If pairing an after market CL350 header pipe with NOS OEM muffler, can one expect this type of hybrid to be working well or will it still be rough because it is an aftermarket header pipe regardless of the OEM muffler?

Thanks again for all of your expertise!
 
Follow-up questions:

Is an OEM header pipe for CL350 "special" or not? It has been mentioned that the OEM Honda exhaust system is less loud and Honda really knew how to design the exhaust just right for flow/performance. I believe its well established aftermarkets are louder consistently and performance not always the best. Is that engineering and performance ALL in the silencer/muffler or the entire length of pipe and silencer? ie If pairing an after market CL350 header pipe with NOS OEM muffler, can one expect this type of hybrid to be working well or will it still be rough because it is an aftermarket header pipe regardless of the OEM muffler?

Thanks again for all of your expertise!

The issue becomes that I find is most people are trying to use shortie mufflers and/or mufflers with little baffling and back pressure.

Many try to use to over sized headers and wide open pipes for looks and they want that little twin to sound like a hot rod. Great for top end performance to a point, lousy for every day street riding where low end and mid range performance is reduced by using wide open pipes and mufflers.

The way the CB/ CL350 engine is designed it likes long headers and a moderate back pressure. It’s been pretty widely accepted that a reverse cone of moderate length can retain the performance and maybe slightly improve the performance over the stock mufflers.

Exhaust science is that, a science. Honda got it pretty damn close when they designed the CB headers. With the CL, performance is lost over the CB due to high, tight bends. If you cut a CL header system you will see that the pipe is double walled off the engine to just below the spark plugs then opens into single wall. I want to say the double wall section ID is actually 1.25” while the single wall section is 1.50”.

I can’t remember the math off the top of my head, do a search on Cone Engineerings site to get a better idea but I used their formula when designing my 2-1 CL header which uses stock headers to just under the sparkplug at 1.25 ID doublewall where it then becomes a 1.5, 1.5 to 1.75 merger then 1.75” to a Cone Engineering 18” Quiet Core reverse Cone muffler that ends. 2” beyond my rear axle.

If you decided to retain the 2-2 header, two 1.5 reverse cone mufflers would be used, not straight throughs, baffled for best street performance.


Sent from my iPhone using Tapatalk
 
IMO the only thing special about the OEM header pipes is they are double wall so the outer pipe doesn't blue the chrome as easily, something Honda did on most of their bikes if not all. As long as the header pipe is the same diameter and length, pairing it with OEM mufflers should work as well as the factory pipes.
 
That's great to know as my pipes I think are fine but aftermarket. My wife had one request when I bought a bike and it be quiet. I should have been more patient and found one with OEM pipes already on. I guess the lower exhaust should be easy to tackle with this piece of information. Upper seems to be another story.
 
Exhaust systems are a science all it's own plus a bit of magic thrown in:lol:
The inner pipe matches the exhaust valve and port diameter so the gas column doesn't expand and slow down. The outer pipe works as an insulation barrier that helps keep the exhaust gasses hot so they don't slow down, side benefit is the outer pipe isn't as hot.
Muffler sizing general rule is 10 times the swept volume of one cylinder, in this case 325cc/2 = 162.5cc's x 10 = 1.625 liters. Coupled with proper efficient baffling and you get good flow plus noise reduction. Cheap mufflers are cheap for a reason, they are built to look nice.
 
...Exhaust science is that, a science. Honda got it pretty damn close when they designed the CB headers. With the CL, performance is lost over the CB due to high, tight bends. If you cut a CL header system you will see that the pipe is double walled off the engine to just below the spark plugs then opens into single wall. I want to say the double wall section ID is actually 1.25” while the single wall section is 1.50”....
The Stock CB headers are also double-walled for a distance after leaving the head. As others have said, in addition to keeping the pipes from discoloring, the smaller ID keeps the exhaust velocity higher, which is a good thing. While the main reason I changed my CL over to CB headers was for ease of air cleaner and carb access, I knew that those headers combined with some longer reverse cone mufflers (with decent baffling) would also provide the extra few horsepower that are typically lost with the stock CL exhaust system. I’ve been very happy with the setup the couple years it’s been this way.

4104B78A-61CF-4639-9F03-D93350DE8415.jpg
 
The Stock CB headers are also double-walled for a distance after leaving the head. As others have said, in addition to keeping the pipes from discoloring, the smaller ID keeps the exhaust velocity higher, which is a good thing. While the main reason I changed my CL over to CB headers was for ease of air cleaner and carb access, I knew that those headers combined with some longer reverse cone mufflers (with decent baffling) would also provide the extra few horsepower that are typically lost with the stock CL exhaust system. I’ve been very happy with the setup the couple years it’s been this way.

View attachment 6460


I probably should have just made the conversion to CB for all reasons you mentioned, but i love the the classic scrambler look. I just pulled the trigger on a NOS OEM lower silencer. Pricey, but what the heck, It's not like I went on a vacation this year. Now the hunt for an upper
D2731D0E-145C-4F14-B125-9ECE7D4DB81A.jpgB8D55E9E-D247-42D2-A442-171EF8BAAD6B.jpg55FC6DE1-0A98-4222-8DFA-BD0917CE8C67.jpg
 
Wow - that's pretty! I think the challenge that you're facing is that the upper/right side is one piece from the head and they're damn near impossible to find in decent condition.

I have been really curious about the insides of those. Any chance you have a scope and can take some pictures of the inside of the muffler?
 
I have been really curious about the insides of those. Any chance you have a scope and can take some pictures of the inside of the muffler?

The scopes run up against a baffle a few inches into the muffler, I wasn’t able to get mine around it, but thankfully what I was looking for (and dreading) was right at the end - enjoy a picture of my cracked baffle =)

20043ca3879155a7071c06fedd4784ed.jpg


I do plan on making the 2-1 conversion for this bike, and when I do it I’ll open this one up if for nothing more than curiousity, and to attempt a repair.


Ed
1972 Honda CL350
 
Wow - that's pretty! I think the challenge that you're facing is that the upper/right side is one piece from the head and they're damn near impossible to find in decent condition.

I have been really curious about the insides of those. Any chance you have a scope and can take some pictures of the inside of the muffler?


I don't have a scope like camera. Hopefully the other message helped.

On the other note re: right upper scarcity . . .well aware, it will be a challenge. What I don't understand since aftermarket right mufflers are basically the same as the left (outside of the heat shield screws being mixed up) why can't one just find another left lower and clamp it on an aftermarket right upper header similar to the lower? Why right and left different on OEM but aftermarkets seem identical?
 
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