Home made DB killer

[Pete.]

Someone I know bought a 3 yr old Yammy R-125 which has a Scorpion pipe on it. Being a mature person he wanted to shut it up a bit since the yoof he bought it from had launched the factory one so that it sounded wikked

So I said I'd make him a DB killer. I just bought a TIG welded and this could be my first non-paying job so it was a bit of fun for me too. Came out reasonably well.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Pete.]

Now the funny thing is, when I made it originally it had a much longer tube and no holes in it - it actually made the bike a LOT louder, like ear-drum-tickling loud. I cut the tube down and drilled the perforations and it was much better.

I did take some video on my phone but the noise-cancelling clipped all the loud bits off
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[CarlosCBR]

Awesome stuff... Fancy a bit of paid custom? In dire need of a baffle, unobtainable in the size I need :/
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https://www.youtube.com/watch?v=1OPv5mDPQ14

https://www.facebook.com/carl.simmonds.7

[Pete.]

What sizes you looking for? I don't do paid work and I only just got started out with TIG welding this week so I can't guarantee results, but if you send me your critical dims I'll see what tube I have got.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[RhynoCZ]

Is the end of it sealed - inner part? If not, then it won't work. The pictures look like you just drilled a piece of pipe.

Check mine (not that nice, couldn't weld thin metal): https://s970.photobucket.com/user/RhynoCZ/media/GPz%20-%20New%20exhaust%20system/Fotografie-0014.jpg.html?sort=3&o=15
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Pete.]

It does work, check out the designs of the ones on eBay. I tried it un-drilled and then drilled and the holes quietened it down a good bit.

I'm surprised yours does with the way you've restricted it. What do you have, a dozen 8mm holes in that? If so that's like having a 28/29mm ID exhaust.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[RhynoCZ]

I made the holes bigger after - tuned it up slowly with bigger diameter of the holes. It gave me low/mid range torque boost and made the bike quiet like an OEM exhaust.

What you did does restrict the exhaust gas flow, but not that dramatically so it'd significantly lower the noise. From my experience it's better to have a bit more noise though. Too restricted exhaust increases the head temperature which is not good. The holes you made have no purpose if the pipe is open.

I checked the google and every single DB-killer there is sealed up.

Anyway, nice work with the welding, what did you use?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[nowhere.elysium]

Rhyno, you're just making yourself look daft. Please stop.
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'10 SV650SF, '83 GS650GT (it lives!), Questionable DIY dash project, 3D Printer project, Lasercutter project

[robocog]

I /think/ I get why it would have been louder when the pipe was longer (and undrilled)

(but not sure if I am able to fully explain in words)
I'll try...

Imagine the tube was even longer - so the pipe was touching the end of the silencer where the exhaust pipe enters

the sound waves would have a direct unhindered route to the outside world - negating the wadding that is behind the oem perf tube and would have little or no effect or even louder than the std can


Making it shorter and holey has made a "trap" that /some/ sound waves will be reflected back into the can - and against the oem's perf tube and wadding

The more convolute the path the sound waves have to take the more silencing the wadding will absorb?

I guess the silencing effect at different rev ranges could be tuned by varying the length of the tube and drillings?
(rather than just an overall silencing effect??)

It's a black art I guess

Regards
Rob
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Needs a bigger garage...

[Tungtvann]

[SQL]

Mine is a sealed DB killer (Not that is it in) and it doesn't seem to make much difference to the sound at close proximity

[Pete.]

[robocog]

I'd be be very interested in your findings

esp just compared to a cap or stub

The ones in the pic Tungtvann posted also look like they have a bend on the end
If this was pointing towards the perf tube and packing I would think it would be muchmuch quieter - unless I am not understanding the images

I have a tig set here (DC only) - very satisfying stuff!
Just watch out for HF zaps , broken a few tunstens and end caps from dropping/lobbing the head (I assume keeping my gloves in metal roofed garage and working on a metal covered workbench is not helping)
Best thing I got for it was a flexible WP17 head and gas lens - ace for getting round tighter stuff with more stickout and being able to angle the head

I considered making a db killer for my GPZ after 1 escaped somewhere on the A32 (after a meeting and someone wanted to hear what they were like without and rather unhelpfully forgot to tighten the allen screws up)

Thing is I didn't notice till I got home and it sounded lumpy/uneven at idle (running twin exhausts)

I just bought another to replace it with as I didn't have any tubing the right diameter and mine is of the sealed type with a rather nice rounded end which I am not confident I could have made

What mine look like
https://i.ebayimg.com/00/s/MTAyNFgxMDI0/z/hEMAAOxycmBS514W/$_1.JPG?set_id=8800005007

Looking at the type you have and those images I'm now doubting that the type mine came with is doing as good a job as it could
I guess the type I have is just reducing the inner space that the sound travels through hoping more gets absorbed by packing?

It could be that mine needs re packing as it does seem much louder than when I first fitted them a few years ago, mainly at higher RPM

Regards
Rob[/img]
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Needs a bigger garage...

[Rogerborg]

How's the fuelling and the exhaust values?
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[robocog]

Is that to me Roger?

Regards
Rob
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Needs a bigger garage...

[Rogerborg]

[Pete.]

Injected bikes commonly run rich when fitted with a more open exhaust. Dunno why but this one is no exception the exhaust was black with soot. I don't know what effect the baffle will have as it's waiting for bits for it's 1st MOT.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Cockercas]

Mine is pretty much the same as that. Unsealed.
105db without
97db with.
At 7k

[stonesie]

Nice work, it looks quite like the OEM Scorpion baffle except that is closed at the end.

https://shop.t3-racing.co.uk/ekmps/shops/t3racing95/images/scorpion-serket-exhaust-baffle-1009-p%5Bekm%5D300x168%5Bekm%5D.jpg

[Pete.]

[Rogerborg]

[Pete.]