1957 Showa 250cc "Cruiser"

[Vincent]

'New one on me this, check out that exhaust

https://i77.photobucket.com/albums/j71/Drewskovitch/Jap%2070s%20bike%20toys/Bike%20toys/1957-Showa-Cruiser%20jpg_zpsqfv6wwia.jpg

https://i77.photobucket.com/albums/j71/Drewskovitch/Jap%2070s%20bike%20toys/Bike%20toys/1957-Showa-Cruiser2%20jpg_zps6fzqzoct.jpg

https://www.motorcycleclassics.com/barbers-best/1957-showa-cruiser.aspx
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[pepperami]

That`s not an ugly looking bike.

as for that exhaust : I seem to remember seeing pipes like that on an old pre-war German bike, so I guess nothing is new. (possibly Adler)
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I am the sum total of my own existence, what went before makes me who I am now!

[Vincent]

Aye......'think it says something about it being modelled on a German bike. All early Jap bikes were a copy of some other machine.
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[Ed Case]

The Royal Enfield 'Flea' (competition (?) to the BSA Bantam) had an exhaust pipe very similar the that.

[Vincent]

[Triton Thrasher]

[stevo as b4]

Very cool bike!
Yeah it looks like a current style 125cc MX expansion chamber design, but I bet they had no idea of dimensions and resonant frequency back then, but wouldn't it be cool if that pipe really works and adds power.

[Triton Thrasher]

[Vincent]

Apparently, expansion chambers were invented by a German in 1938 to help with fuel consumption rather than power.....although they're connected to some degree I guess. Looking at the Showa bike, maybe stingers were yet to be invented.

https://en.wikipedia.org/wiki/Expansion_chamber
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[RhynoCZ]

Expansion chamber exhaust systems were invented/first time used on the track by MZ, you can even see the lack of Japanese two strokes before that time period and the Japanese crazy fast revving 4 strokes.

And as always, Japanese manufacturers took all the European ideas, not giving a feck about any patent laws, and coppied it so well, the final product was even superior to the European original.

The Showa Cruiser is made in Japan, in that time period (50's to late 60's), so it is in fact a copy of generic motorcycles that you could see here back in the day.
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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

[Triton Thrasher]

MZ's designs were stolen by their East German rider/engineer Ernst Degner, when he defected (during a race) and joined Suzuki.
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[Ed Case]

[RhynoCZ]

[Vincent]

From the youtube clip:- "Harmonic chamber"......love it

har·mon·ic (här-mŏn′ĭk)
adj.
1.
a. Of or relating to harmony.
b. Pleasing to the ear: harmonic orchestral effects.
c. Characterized by harmony: a harmonic liturgical chant.
2. Of or relating to harmonics.
3. Integrated in nature.

'Got that right.
'Nothing to do with mechanics really.....two stroke exhaust tuning....and I never got my Physics level

So why have the chamber nearer the cylinder Or does it not matter and just a question of where it fits?
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[RhynoCZ]

Looking at this simple diagram, I'd say it does not really matter where the chamber is. But, I don't know much about two stroke efficiency.

https://upload.wikimedia.org/wikipedia/commons/5/52/Arbeitsweise_Zweitakt.gif
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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

[Kickstart]

Hi

Expansion chambers are complicated things that virtually nobody understands well enough to come up with designs that work well.

But yes the distance to the expansion chamber is critical.

All the best

Katy
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Vincent]

The few "things" I've learned about expansion chambers over trhe years:-

1; They sound good
2: They sound even better if they're made from stainless steel but SS pipes don't perform as well on race bikes.
3: The downpipe part...ie, the first ...say 6 inches from the cylinder...needs to be conical. You see some pipes where they've just welded a normal tube onto the first part of the pipe and apparently that's not good.
4: Generally, a thinner chamber will perform better at high revs and the fatter chamber will gain torque at lower revs.
5: They sound good...did I say that already?
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