Topic: Louder and more masculine sound with stock pipes ? // re jetting ?

[Viktor.J]

Hello !

To start with i want to say that ive tried the search function without any good resault, so if this subject is already cleared out, please give me the link and discard this thread !

Now to the subject:
Im going to run my CB750 K2 with the original stock pipes (OC they are the most beautiful 4-4 exhaust ever). BUt i want a little bit more aggressive and darker sound. I dont really like the 4-1 no baffle sounds.. sound just like a old Volvo racing (no hard feelings), but in my opinion it sounds a bit "cheap" and "noicy".
I Would love the original sound if it wasn't for the fact that its a little bit to quiet, I would like a little bit more "UMPH" and "Roar". a little darker and louder tune !

Which is the best way to make this ?

Remove the baffles totally ? ive searched the internet for a stock pipe without any baffles sound, but no luck.
Maybe "lighten" up the original baffles ? remove some "damping fabrics" or whatever it is that's in there ?
Any body else with stock pipes and a little bit more masculine sound ?

Do i need to re jet the carbs ?




please, any input you have !

// Viktor

 

[ekpent]

Here in the US the 72 came with the #341 pipes. Unlike the #300's on the earlier bikes that had a real baffle, the 341's do not have a baffle per say but just a diffuser on the end of the pipe,maybe to keep a mouse out. Most of the baffling is from the interior chambers that are built in. For a stock look and a more Manly sound you need to go with the 300's and leave the baffle out 
  Edit-Here are some pics Vik to explain a little better. First pic is the later,72 and later 341 diffuser and the second pic are the #300 real baffles from the earlier machines.

[TwoTired]

I Would love the original sound if it wasn't for the fact that its a little bit to quiet, I would like a little bit more "UMPH" and "Roar". a little darker and louder tune !

Which is the best way to make this ?

Impossible to make it "too quiet".  But, perhaps you like to wear bright red cod pieces?   What is a dark sound?  You want a dirge sound?
Kinda seems you want to make it sound like a larger displacement bike.  There is no replacement for displacement.  Perhaps you could search for and install a 1080cc conversion?

Otherwise, an MP3 player, an amp, and speakers.

Do i need to re jet the carbs ?

Not with an MP3 player!   

If the carbs are stock and with stock settings and adjustments, to get it to run as sweet as stock with exhaust mods, means at least some carb adjustments need to be made.
Kinda depends if you are happy with it running and making lots of noise vs. running as well as when stock at all RPM ranges.  Of course, if you are an expert carb tuner, then it can be done with money and time spent.

Your money and time, so best of luck to you!

Cheers,   

[Stev-o]

Eric - do you know is those 341 "diffusers" still available from Honda? Thx

[Viktor.J]

Eric - do you know is those 341 "diffusers" still available from Honda? Thx

Whell they aren't exactly cheap http://www.davidsilverspares.co.uk/CB750K1-FOUR-1971/part_104603/
http://www.davidsilverspares.co.uk/CB750K2-FOUR-1972/part_104939/

[madmtnmotors]

What could be more masculine than walking softly and carrying a big stick?

[Viktor.J]

Haha i feel that i want to correct myself

By more masculine sound i dont necessary mean that i have any inferiority or problem with my one sexuallity 
I was just trying to explain (in many ways) the sound i was looking for

What could be more masculine than walking softly and carrying a big stick?

Well probably nothing, but if you also want to ride your bike, then you have a problem mr. 

Impossible to make it "too quiet".  But, perhaps you like to wear bright red cod pieces?   What is a dark sound?  You want a dirge sound?
Kinda seems you want to make it sound like a larger displacement bike.  There is no replacement for displacement.  Perhaps you could search for and install a 1080cc conversion?

Otherwise, an MP3 player, an amp, and speakers.

If the carbs are stock and with stock settings and adjustments, to get it to run as sweet as stock with exhaust mods, means at least some carb adjustments need to be made.
Kinda depends if you are happy with it running and making lots of noise vs. running as well as when stock at all RPM ranges.  Of course, if you are an expert carb tuner, then it can be done with money and time spent.

Your money and time, so best of luck to you!

Cheers,   

OF course i could bore up the engine, change bike or buying myself a gasturbine for that extra masculine engine sound But this question was about doing some modification to the original bike, and stock pipes to maybe make the sound a bit more free, And i dont want it to be loud, just louder with the same "sound".

Like if stock pipes are 40% and 4-1 without baffles are 100% i would like 60% with stock type sound

Here in the US the 72 came with the #341 pipes. Unlike the #300's on the earlier bikes that had a real baffle, the 341's do not have a baffle per say but just a diffuser on the end of the pipe,maybe to keep a mouse out. Most of the baffling is from the interior chambers that are built in. For a stock look and a more Manly sound you need to go with the 300's and leave the baffle out 
  Edit-Here are some pics Vik to explain a little better. First pic is the later,72 and later 341 diffuser and the second pic are the #300 real baffles from the earlier machines.

These #341 pipes with the interior chambers, if they do the most diffusion of the sound, then by removing the last diffusors would make it a little bit louder, since the "internal baffles" reduces noice.... ?

[ekpent]

Eric - do you know is those 341 "diffusers" still available from Honda? Thx

Hey Steve'o,I lifted both of those pictures from current E-bay auctions but did not notice how much they were. Checked my local shop here in Kazoo,Cyclepartsnation on the web and see I can get them, I think, for $21.21 each with free shipping.Nice to be able to pick up there as I hear their shipping charges are steep,can take stuff back which is even better. Luckily for NOS its easy here.

[Stev-o]

Good to know, Eric, thx.

I bought a K6 for cheap and it has a decent set of stock pipes...but no baffles.

[Viktor.J]

Steve-o how does it sound compared with one with baffels ?
 

[ekpent]

Steve-o how does it sound compared with one with baffels ?
 

I will chime in on that if I may and with the diffusers out its not very much louder on the 341's.  Not a whole lot more Masculine---Sorry Vik could not help myself   

[Stev-o]

Steve-o how does it sound compared with one with baffels ?
 

I bought it as a project bike and have not attempted start up yet. [presently working on a K2]

[madmtnmotors]

What could be more masculine than walking softly and carrying a big stick?

Well probably nothing, but if you also want to ride your bike, then you have a problem mr. 

Just waxing metaphorically, and improperly quoting the 26th President Theodore Roosevelt: "Speak softly and carry a big stick"

    Where "Speak softly" would refer to quiet pipes (I'm a big fan) and how much bigger stick do you need than the "Motorcycle of the century" CB750...

 

Although, the 60% sound level you describe is probably quieter the the 4 into 1 Mac pipes I currently have installed (and would like to make quieter by the way...), sorry I don't have any first hand experience with modifying the stock pipes and baffles.

[BobbyR]

The one problem you run into is that these are 4 cylinder engines. They have two extra beats compared to a big twin or a 750 twin for that matter.  It will always have the Volvo sound. 

[killersoundz]

Yup. The best sound from a cb750 IMO is a 4 into 1 header straight with no muffler. Terminating at the end of the 4 into 1 collector, with the pipes wrapped with exhaust wrap. Deepest and most lively sound you can get out of these.  A 4 into 1 header straight sounds like a F1 car while if you run these with 4 into 4 straight pipes it sounds like a lawn mower.....4 into 2 straight sounds cool especially the cross over 4 into 2 pipes that put 1 and 4 on the left side and 2 and 3 on the right side.

[Stev-o]

The one problem you run into is that these are 4 cylinder engines. They have two extra beats compared to a big twin or a 750 twin for that matter.  It will always have the Volvo sound. 

Volvo?!  [never had one]  I'd like to think my K4 sounds better than a Volvo!

My stock K8 is too quiet, IMO. But I don't want to mod it.

[ekpent]

When my 71 gets on the pipe good with its stock 4 piper it can get a little attention out there,it wails nice and rich,especially at around 5,000 +.  4 holes are better than one   

[DJ_AX]

You can make any muffler sound more masculine... just twist the throttle more!

[750K]

The one problem you run into is that these are 4 cylinder engines. They have two extra beats compared to a big twin or a 750 twin for that matter.  It will always have the Volvo sound. 

Volvo?!  [never had one]  I'd like to think my K4 sounds better than a Volvo!

My stock K8 is too quiet, IMO. But I don't want to mod it.

The pre 75 b18-b20 actually do sound like an inline 4, my old 66 & 67 volvo wagons were louder than my buddys cb400f but had a similar note. They both would trip car alarms, miss those cars.

[jason41987]

i was always under the impression that SOHC/4s were a much higher revving engine of lower displacement per cylinder which would result in a higher pitched sound in general comparison to a 2-cylinder bike of similar displacement?... am i wrong?.. meaning, wouldnt it be easier to get a CB550 to sound like a ricer, or v12 supercar than it would be to get one to sound like more like a little muscle car whch is an analogy for the direction it seems the OP is trying to go with the sound?

one thing i noticed though... im not sure if this is just a wrong impression or if others have the same opinion about it as i do.. but to me it seems the 4-into-1 exhausts have a higher pitched, more monotone sound compared to CB550s that use a 4-into-4 or even 4-into-2 exhaust?.. i could be wrong, but thats what it seems like to me

[Viktor.J]

Steve-o how does it sound compared with one with baffels ?
 

I will chime in on that if I may and with the diffusers out its not very much louder on the 341's.  Not a whole lot more Masculine---Sorry Vik could not help myself   

HAha, the jokes on me I guess, im blaming the english since its not my mother tounge. In swedish masculine is a commonly used adjective

But maybe thats the sound that im searching for, as said i dont want much louder, just a little tweek

[Viktor.J]

I have removed the baffles now. Somehow the microphone on my camera couldnt capture the sound really accurate. IT SOUNDS a little bit more then what the videos "shows". Does anyone now if there's any need to change the jet  ?

Anyway to get rid of the "bangs" as the rev going down ?

With baffles:
CB750 original exhaust with baffels

Without baffles:
CB750 original without baffles
CB750 original pipes no baffles

[Viktor.J]

I dont really know how to translate this to english... But here it goes..

As you can see by the previous posts I've removed the baffles and it gives a little more louder and sweeter sound, I'm satisfied !

When I release the throttle / rev down it bangs/fire/shoots in sweden we call it "carburetor bangs/explosions". Ive understood that this could be to small "low jet size" ?
Any ideas ? On how to get rid of these bangs ? I don't want to run a poorly tuned engine

[Xnavylfr]

Try closing /screwing IN your air screws about 1/4 turn.  As you allow more exhaust air OUT( opening the exhaust up) it pulls more air in so you need to restrict the amount air a little.
Anytime you put OPEN exhaust/ straight pipes/NO baffles it causes the engine to run lean and you MAY need to fatten ( GO LARGER) on your jets.
Re-set the air screws then do some plug chops!  If the electrodes on the plugs are real white, then the bike is still too lean.


Xnavylfr(CHUCK)

[Viktor.J]

Try closing /screwing IN your air screws about 1/4 turn.  As you allow more exhaust air OUT( opening the exhaust up) it pulls more air in so you need to restrict the amount air a little.
Anytime you put OPEN exhaust/ straight pipes/NO baffles it causes the engine to run lean and you MAY need to fatten ( GO LARGER) on your jets.
Re-set the air screws then do some plug chops!  If the electrodes on the plugs are real white, then the bike is still too lean.


Xnavylfr(CHUCK)

Thanks for the input, that makes really sense
By "go larger on your jets" do you mean main ? slow ? or what jets ?
Im gonna take a ride tomorrow and then check the plugs, thanks !