Opening up OEM muffles? - Honda Valkyrie F6C Forum
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post #1 of 10 (permalink) Old 09-05-2018, 11:56 AM Thread Starter
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Opening up OEM muffles?

Hi,
Really like the look and size of the standard exhaust set up, dont particularly want it 'louder' but I am considering opening up the two sealed exhaust pipes (per muffler) by drilling them out. I have done similar on other bikes before and due to the catalyst there's not a great deal of extra noise but I am thinking surely less restriction will let it breathe more easily?

Has anyone done this? Did it go ok or was it a pig to do? Looks like access is pretty easy. I can't really work out what the exhaust flow is and whether infact these blocked pipes are just dummies and do nothing.

Would appreciate any thoughts from the forum.
Kind regards john
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post #2 of 10 (permalink) Old 09-05-2018, 09:53 PM
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Just buy Torquemasters and spend the money. If you happen to mess up your stockers it'll be tough finding replacements cheaply due to the rarity they come up. And buying from Honda? It'll be an expensive experience.
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post #3 of 10 (permalink) Old 09-05-2018, 10:25 PM
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Others have done it and said it sounds like a leaky exhaust. Here is a video of one.
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post #4 of 10 (permalink) Old 09-06-2018, 10:58 AM Thread Starter
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Update - firstly thank you for replying. I have just been in the garage and drilled out the dummy exhaust bungs. Took about two hours. Definitely a measure twice cut once job. It went very well but having done this a few times now its extremely easy to make a mess of it so patience is a must. I used a good quality 1 inch metal hole cutter NOT a drill bit. The stainless metal used for the bung is quite thin (thankfully because its very hard) and cut out very neatly. So what difference......not much TBH. Sound is a bit deeper. Not sure if anyone is interested but now that all three outlets are clear i can see into the muffler and see what the flow path of the exhaust gas is.

As standard there is only one inlet into the muffler (from catalyst side), that goes into one pipe (the outer one as you look at the bike from the back end) which is drilled along its length and bunged. That forces the gas sideways into the top tube (which is also bunged) which forces the gas to run backwards down the top tube where its open ended inside and that allows the gas into the bottom tube and out it comes. Sorry if that is confusing but hopefully you get the gist.

In simple terms the exhaust gas is turned 180 degrees on itself and reversed then once more 180 degrees and it comes out. All inside the muffler.

Am i pleased i did it? Yea, because it would have bugged me. Do i expect any performance gains? No not really, probably not made a jot of differnce.

After opening all three holes on mine two of them are essentially redundant now because the gas just comes straight out of the one (outer) pipe. There is literally nothing to cause the gas to use tubes two and three anymore.

All tubes are the same diameter so there you go. Hope someone may find this useful.

Kind regards john
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post #5 of 10 (permalink) Old 09-06-2018, 11:15 AM
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This has been experimented with at length.....Most have decided that cutting a 1/2" hole in each of the dummy plates got the best sound. A little deeper at idle & a little more scream WOT ....... I did this to mine ,No leaky exhaust sound & not too loud or drone .......
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post #6 of 10 (permalink) Old 09-07-2018, 01:05 PM Thread Starter
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In my last reply I described the top tube as being a pipe inside, its not its more of a chamber. I got confused so apologies for that. Just incase anyone also chooses to do it. By the way i have just been out for a ride. It sounds Royal. Deep, burbly, very pleasing to the ear indeed.
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post #7 of 10 (permalink) Old 09-10-2019, 12:23 AM
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Originally Posted by jfro5867 View Post
In my last reply I described the top tube as being a pipe inside, its not its more of a chamber. I got confused so apologies for that. Just incase anyone also chooses to do it. By the way i have just been out for a ride. It sounds Royal. Deep, burbly, very pleasing to the ear indeed.
Do you have an audio clip of this new sounding exhaust? I'm interested!
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post #8 of 10 (permalink) Old 09-10-2019, 10:34 PM
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This has been experimented with at length.....Most have decided that cutting a 1/2" hole in each of the dummy plates got the best sound. A little deeper at idle & a little more scream WOT ....... I did this to mine ,No leaky exhaust sound & not too loud or drone .......
This sounds very easy but I'd love to hear a comparison. Do you mean 2 holes total (as in 1 on each side of the bike, maybe in the middle of the dummy plate that holds all 3 outputs), or 4 total (one in the middle of the dummy plate in each fake tailpipe)? What would be the easiest drill bit to use for 1/2", I guess a small donut hole cutter designed for metal (Do they even make such a thing?

Previous owner of my other bike had simply drilled the stock pipes and I liked it and received compliments, then I came across a set of cobras, installed then with the corresponding carb jet kit, and I liked it less, as I don't want to wear ear plugs inside a full face helmet when I ride. Thinking of trying a smaller hole size first that can be gradually enlarged as you can't easily go back.

At 8800 miles, mine does seem to be getting throatier with time, and I like that.

2nd owner of 2014 Valkyrie

Previous Bikes:
66 Benelli (Montgomery Wards) 125 cc Riverside
74 Yamaha Enduro DT360
74 Honda CB450
76 Kawasaki KH500
77 Yamaha RD400
80 Kawasaki KX250
71 Honda CB750K1
82 Yamaha Virago XV750
'95 Honda Magna VF750CD
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post #9 of 10 (permalink) Unread Yesterday, 05:26 AM
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Two holes only,first layer only. Not through second plate. This is for each muffler for a total of four holes. Good quality 1/2" bit will work fine......

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post #10 of 10 (permalink) Unread Today, 05:41 PM
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all new exhaust systems, aftermarket as well are bit tinny sound when new. this is fresh bare metal. after a good amount of miles they will coat up with carbon and the sound will deepen. they ALL do this. stock and aftermarket.

stock mufflers are not anything like after market mufflers which tend to be straight thru flow design with expansion areas and very often glass packed.
stock mufflers utilize 3 separate expansion chambers such that gases flow from the inlet to the first chamber, expand and then flow thru a small dia pipe to the last chamber and expand again, and then flow backward to the middle chamber expand before reversing flow once again and exiting out the back of the muffler via a small aparature opening, significantly smaller than the diameter of the muffler.

so drilling out those dummy nipples just exposes the 2nd stage area to exhaust and bypasses the middle chamber which is 3rd stage expansion. this is why they most always sound funky, you are getting all kinds of non laminar flow thru the rev range.

if sound is what you are after, you are better off with just a long straight piece of exhaust pipe w/o muffler. the longer the better. it is like a wind instrument. varied lengths, varied velocities, produce different pitch.

Ursus Horribilus
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