Alternative spannies?

[pepperami]

Yes Yes I am searching the net, but I thought I`d just ask anyway .

So I have an old Jawa 350 twin that will be my long term project.
I recon this one might take a couple of winters to put straight .

So at the moment I`m at the pulling apart stage and investigating the insect nests I keep finding every time I remove a bit of the bike
I`m also buying little bits and pieces I am going to need.

As anybody knows who`s had anything to do with Jawas/CZ`s, the exhausts weigh as much as a small bus!.
So I`ve been having a think about putting a set of spannies on the bike?
Any thoughts peeps of the mighty BCF?
I have a MIG welder so some very simple fabrication/joining is a possibility, maybe, I hope.

I`ve seen it done before where the chap had re-jigged an old set of after market Suzuki GT 250 spannies and the bike went reasonably well.

What do you think? do you think it is worth trawling the bike jumbles or do you lot know a supplier at a reasonable cost?
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I am the sum total of my own existence, what went before makes me who I am now!

[temeluchus]

https://www.jawamarkt.cz/en/jawa-cz-250-350ccm-/exhaust-2-2
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Some shite cruiser. Now with guns and FREEDOM!

[YBR Ric]

The current 350 jawa comes with an optional factory upgrade
https://www.jawamotorcycles.co.uk/images/expansion_exhaust.jpg
£300.

[pepperami]

Thank you for that peeps any more anybody?.

£ 300 for a set of spannies , the pipes would be ten times the worth of the bike , mind you at least they would fit.
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I am the sum total of my own existence, what went before makes me who I am now!

[stinkwheel]

What I always considered doing, but never did (and as far as I know, has never been done) was to fit a couple of MZ 125/150 exhausts to a Jawa.

You'd need to have a bit of a fanny with the bracketry but those stupidly long, heavy exhausts MZs have fitted are mathematically perfect care of Walter Kaaden and they're about the closest thing I could think of to half a Jawa engine in terms of bore, stroke and rev range.

Even MZ TT racers and their works trials bikes had the same exhaust fitted.

Weight saving will never gain you much in terms of performance on a Jawa, it will always weigh as much as a small tank. A set of intelligently designed spannies might gain you some power and throttle response.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MarJay]

[stevo as b4]

Marjay, i agree if your looking for the optimum exhaust for maximum possible performance, with what you said.

But if your just wanting to cobble on an alternative exhaust or fit an expansion type exhaust to commuter 2t etc, then basing the exhaust on an expansion chamber of another bike with the same cylinder capacity is IMO the best starting point. I think you will find that the required total pipe volume changes more with cylinder capacity than it does with state of tune, and port timings etc etc.

That is why for example that Kawasaki AR125 pipes seem to work ok on a KH125, or RG250 pipes can work on an X7 or GT250 etc. They will not be the optimum pipe for another engine that's tuned differently, but using a different pipe from another engine with the same capacity is id say the best starting point if your experimenting with a performance exhaust for a bike that never had one fitted or has any aftermarket options.

BTW alot of the big name expansion chamber manufacturers for the popular 80's- 90's sports 2strokes, did less R&D than you might think. If they weighed less, sounded better and made the bike feel more peaky they were often considered a success, and it's relatively easy to improve the performance from a std factory pipe slightly, without ever getting close to an optimum design. Some pipes were made with big dents in them shaped to fit the bike or for them to clear the swinging arm etc.

If your expecting anyone to sit down and roll up cones to make 1/2 a dozen prototype pipes, or spend ages stripping down engines to measure every dimension and clearance to feed into expensive complicated computer design/simulation propgrams then i think you've missed the point somewhat if im honest!

[hmmmnz]

if you can weld, or atleast can cut steel and tack, and don't mind a bit of maths, then making up a set would be your cheapest option and then getting someone to weld them, its not hard to roll a bit of flat steel,
but as for easy, buys a set direct from jawa is always easy... just costly
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I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[stinkwheel]

[pepperami]

I did think about an old set of RD 350 lc pipes?

A couple of times when I`ve been round the bike auto-jumbles, I`ve seen a set for sale.
I`ve always held back from buying them because it would seem like sacralige cutting them up to fit an old stinky Jawa?
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I am the sum total of my own existence, what went before makes me who I am now!

[stevo as b4]

I assume you mean aftermarket 350LC pipes? As cutting up a set of the prized holy grail (but ugly as hell) std pipes would have you shot and killed and then set on fire while hanging from a tree, by all the RDLC freaks/enthusiasts out there!

[pepperami]

No, that`s the point, Twice when out on the bike auto-jumbles I have found standard 350 spannies for sale at a price I could afford.
But I just could`nt buy them just to chop them up, even I`m not that much of a philistine!
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I am the sum total of my own existence, what went before makes me who I am now!

[N cee thirty]

you won't get any rd pipes cheap now

try mick abbey, he might do you some for under £400
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

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