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  1. #1
    Senior Member cosmikdebriis's Avatar
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    How To... Arrow Exhaust DB Killer removal and modification.

    This thread is in two parts. The first is simply how to remove/replace the DB Killer (that's a baffle to us old guys).

    The next part will deal with my ideas to modify the original design to make a variable sound DB Killer.

    DB Killer Removal/Replacement.

    Pcture 1

    First job is to pry off a little tag that has been spot welded to the silencer. I'd guess this is to conform to some sort of legislation so be wary of any legal implications it's removal may have.
    Just wedge a small screwdriver under it and tap it with a hammer. It's only held on with a very light tack weld.



    Picture 2

    Next you need to remove a fairly large circlip so use a decent set of circlip pliers. Once you have removed the circlip you can simply withdrae the DB Killer using long nose pliers or similar.



    Picture 3

    Picture showing the baffle removed and... no... there aren't any prizes for the first person to say " my wife has one of those in the bottom of her knicker drawer ;-)

  2. #2
    Senior Member cosmikdebriis's Avatar
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    Part 2... Ideas on DB Killer modification

    Ideas on DB Killer modification

    The basic idea is to come up with a method of being able to increase the volume coming from the silencer but without completely removing the DB Killer. Also, with the ability to fairly simply manually vary the volume level according to your requirements.

    The standard DB Killer is a fairly simple tube, blocked at one end, with a series of holes drilled in it to let the exhaust gasses (and therefore volume) out.

    Obviously the more or larger the holes the more volume would be produced.

    As you can see from the accompanying pictures the original holes are towards the inner end of the DB Killer.

    The idea is to drill some more holes in the original DB Killer but then cover those holes with a metal sheath (bit of pipe). (see second pic) Then drill some more holes in the sheath so that, as the sheath is rotated (manually) the holes line up more or less letting more or less volume out.

    Quite a simple thing to do in theory though the mechanism needed to rotate the sheath will need some thinking about (I have an idea).

    Simplicity of design is the key here so I'm trying to keep things easy to manufacture for even the novice mechanic,

    Picture 1

    Showing the baffle with proposed additional holes. (Experimenting with size and position of holes may be worth pursuing).


    Picture 2

    Showing (badly drawn) metal sheath (basically a bit of suitably sized aluminium or stainless tube) with some extra holes drilled in it. Rotating (or perhaps push/pulling) the sheath will line these holes up with the ones in the DB Killer allowing more volume out.



    Things to consider include the materials used for the sheath and it's relative coefficient of expansion as the sheath may become stuck if it becomes too tight on the DB Killer. Alternatively, if it is too loose it will let out unwanted noise.

    Using different size and possibly shape of hole may well affect the sound.

    Constructive criticism/thoughts on improved design welcome

  3. #3
    Member Livestrong's Avatar
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    That's a good idea! But what if you cut of the top of the db killer? Or maybe begin by drilling a hole in the top?

  4. #4
    Senior Member cosmikdebriis's Avatar
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    Quote Originally Posted by Livestrong View Post
    That's a good idea! But what if you cut of the top of the db killer? Or maybe begin by drilling a hole in the top?
    I want to do it so that it is adjustable so just adding holes won't work (though it would certainly get louder).

    You have however inspired me to a different idea...

    Below is a picture roughly explaining it.

    This time we drill holes almost the entire length of the BB Killer and then manufacture a plug to insert up it. The further up it goes, the more holes are exposed and the louder it gets. If we used threaded bar for the plunger rod and an internal thread on the plunger disc it should be possible to screw the disc backwards and forwards. A bit more complicated to manufacture though?


  5. #5
    Senior Member cosmikdebriis's Avatar
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    DB Killer Mod continues...

    The Disclaimer... (ignore at your peril).
    The following is only a guide and I do not advise anyone to copy my design. I can and will not accept any responsibility for ANY harm caused to you, your bike, your friends, neighbours, small furry creatures, passing aliens or the England football team.
    This modification may well affect your bikes warranty, cause damage to your bike, make the bike illegal for road use cause a third world war or even (due to the butterfly effect) be the beginning of the end for our planet.
    Should you choose to follow this design you do so at ENTIRELY YOUR OWN RISK.


    I should say that this is still very much in the experimental stage and so I've been using scrap materials rather than buying new metal. As such the sleeve in the pictures is actually made from an old fork slider I had lying around and I turned it in my lathe to fit. With the proper sized bit of pipe the whole process would be much simpler.

    Picture 1...

    The first picture shows the component parts labelled as follows.

    A). The original DB Killer (modified)
    B) Slot machined in to DB Killer to accommodate screw (E)
    C) New holes drilled through DB Killer (they go right through)
    D) Original holes in DB Killer
    E) Screw (4mm) used to locate and allow partial rotation of sleeve (F)
    F) Newly made Sleeve that fits over the original DB Killer (A)
    G) Hole for screw (E)
    H) Holes drilled in sleeve to match the new holes drilled (C)



    Picture 2...

    Shows the whole thing assembled with the holes lined up and also blocked according to the rotation of screw (E) in the slot (B). Of course you can also partially line up the holes to vary the effect.



    I'll test it tomorrow when it's daylight.

    UPDATE

    Tested and it works... Yippee...

    I'd say I get about a 30% volume increase with the holes fully lined up and this can be decreased back to "normal" incrementally using a pair of long nose pliers and with the whole thing in situ.
    I'm not entirely happy with the adjustment mechanism so may do some more work on that.
    I've added six holes though it would be simple to add more (or less) to suit your taste.
    The sound itself gets "deeper" with the holes aligned which is a bonus.
    I will try and take a video as soon as possible but don't have state of the art recording equipment so sound quality may be poor.
    Last edited by cosmikdebriis; 06-28-2014 at 01:56 AM.

  6. #6
    Senior Member cosmikdebriis's Avatar
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    Further ideas to modify the sleeve...

    In order to make it easier to regulate the increase in volume level I am going to experiment with elongating the slots in the sleeve (with a file) so that they progressively line up with the holes in the baffle.

    The picture below should explain (hopefully).


  7. #7
    Senior Member cosmikdebriis's Avatar
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    I have now made two fairly simple videos of (not me at all) riding my bike with and without the standard Arrow DB Killer.

    Reason I made two videos is so that, if you want to compare, you can open both in different pages and view them together.

    Obviously it wasn't possible to do an exact comparison, not least of all due to the traffic.

    Quality isn't exactly brilliant but I wasn't in control of the camera, and anyway, it's the sound we're interested in and not the riders short fat hairy legs.

    Didn't rev the bike above about 7k and was within the legal speed limit at all times but that better represents "average" usage. The traffic is a bit annoying but it does at least allow for a comparison with ordinary traffic (apart from the Subaru perhaps).

    And yes... I know the rider that wasn't me is wearing inappropriate riding gear but it was so bleedin' hot.

    I can only add one video per post so next video will follow shortly

    Last edited by cosmikdebriis; 07-03-2014 at 02:29 PM.

  8. #8
    Senior Member cosmikdebriis's Avatar
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    And now with DB Killer removed


  9. #9
    Member Livestrong's Avatar
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    I've installed the Arrow exhaust today and it's really difficult to make a choice, with or without DB-killer.
    With, the sound is ok but not "wow"
    without the sound is superbe when you're not on the bike, on the bike it's a bit to much I think.

    What are the options now? putting back or adjust the killer. Or riding with earplugs, this brings me to an other question, is it strange to ride with earplugs?

  10. #10
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    I've been riding with earplugs for a few years now after a friend advised me to do so for the sake of not going deaf...

    Must say I much prefer it and only ride without if I'm doing the daily commute in town (low speed) I find now that it's uncomfortable riding at speed without them. You still hear the revs and everything going on around you, just quieter.

    Although I would only recommend the max lite plugs (soft pink ones or the yellow/pink ones) others are too hard. I use them offshore also and they are great for all day.

    never use the silicone or putty moulded things (too many people have had them break off and get stuck in the ear canal)

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