DIY Spannies..?

[A100man]

Anyone had a go? Thought it could be a 'fun' project to make something for the GT.

Some guidance and even a spreadsheet to calculate dims on this site...

https://www.mopedarmy.com/wiki/DIY_expansion_chamber_exhausts
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[Riejufixing]

[redeem ouzzer]

No. They’ll be shit. You can get a set made by a clever man with a dyno and access to Torquesoft or similar for under £500.
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Be a REAL MAN!

[ThatDippyTwat]

Aside from the physical aspect, there's a fuckton of details with working out the size, shape etc. I'd want a specific set of plans to work to - a change in shape will drastically change where your peak power is, or more importantly, isn't.
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'98 VFR800 (touring) - '12 VFR800 Crosrunner (Commuting) - '01 KDX220 (Big Green Antisocial Machine)

[A100man]

[stevo as b4]

Total minefield and even if you can make accurate cones and weld, it's hours of work for an uncertain or unwanted result in many cases.

I know fuck all about two strokes, but from what I've read many of the programs available for exhaust design are variable and of limited effectiveness. If your looking to make a one time set of pipes and fit and forget you'll be spending all that time for a possible poor result, or even make a bike un-rideable in extreme cases.

Trial and error and experience will get you so far, and if you were willing to make say 5-6sets of pipes and dyno test them, back to back then you might get a good result. Of course many even simple expansion chambers may work better that a straight pipe of the wrong diameter or length, and some will get you a power gain, which might be good enough for the work involved?

And of course not everyone wants a pipe for ultimate power, some people want a certain sound or a classic 70's/80's look, and there's pipe companies catering for this demand in some cases.

Also remember that pipe design between a book written in say 1975 and one based on 2005 moto GP knowledge and development will be vastly different.

I've had a custom pipe built for under £330, but when you think of the design work, knowledge and technology/software involved not to mention the fabrication and fitment to the bike then it was a bargain IMO.

Tl:Dr it depends on what you want to achieve and how much time, effort and skill you have, and how much of a desired outcome you have for it.

[ThatDippyTwat]

[Easy-X]

Funny, was reading through the Yamaha shop manual for 2-strokes (1969) and, to my surprise, they had a whole section on these sort of exhausts (along with other modifications) and gave dimensions for how to make the exhaust for various models... for a 50% example race tune.

Looked like a shed load of work!
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[redeem ouzzer]

Basically the result will be worse than the standard pipes for a shitload of effort and therefore not worth doing. Most "off the shelf" expansion chambers (Micron / Allspeed / Swarbrick etc..) are shit as well.
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Be a REAL MAN!

[Sister Sledge]

[redeem ouzzer]

[A100man]

Ok then chaps, get your silk (polyester) scarves, denim cut-off and fisherman's socks out..

Welcome to 1980...

https://www.suzuki-gt.co.uk/images/Reference%20Library/250%20Shoot%20Out-3%20Part.pdf
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[Easy-X]

[Tankie]

You forgot the seaman's jumper
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Always learning, everyday is a school day