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are there any under square il4 4t engines?

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trevor saxe-coburg-gotha
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PostPosted: 06:50 - 09 Jun 2019    Post subject: are there any under square il4 4t engines? Reply with quote

Has anyone ever developed and sold a four cylinder (in line or V, or other config) engine for bikes with a stroke that's bigger than the bore? I haven't looked but I'm guessing the Ariel was like that. But what about Japanese stuff? I don't think they have - but then again, they seem to have tried (and sold) every viable variant. I know absolutely fuck all about this stuff but if they haven't, I'm guessing that's because performance has always been the primary consideration.

And the assumption I'm making there poses various other questions - one of which is this: are long stroke and/or under-square motors necessarily more reliable and, or, longer lived? Guessing again, I'd say not - but that because they'll generally rev slower they could be thought of as under-stressed.

I suppose what happened with the Japanese manufacturers was that they reckoned that if they could make over square lumps that were good for over 100k miles, long stroke stuff could fuck off.

Some of these thunkages came along after watching a youtube upload on the chrysler slant 6.

https://www.youtube.com/watch?v=b8Y96xywS-E
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GT200Fan79
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PostPosted: 07:48 - 09 Jun 2019    Post subject: Reply with quote

Not a clue on your question but I’ve just binge watched the same series on YouTube. Fantastic to listen to a guy who knows his subject inside out.
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stinkwheel
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PostPosted: 08:56 - 09 Jun 2019    Post subject: Reply with quote

My understanding is that there was a "figure" for maximum piston velocity that "everyone" knew about. Everyone that is, but Japanese piano makers.

They started making bikes that comprehensively blew that "Can't go any faster or the rings will weld themselves to the bore". Figure out of the water through pure ignorance and have never looked back.

In answer to the OP. An Indian 4 has a 2.75" bore and 3.75" stroke.

The Munch Mammut 2000 is exactly square. 86.0 x 86.0.

A Brough Superior Golden dream is also exactly square with a horizontally opposed 4 rather than inline.
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Last edited by stinkwheel on 09:02 - 09 Jun 2019; edited 1 time in total
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trevor saxe-coburg-gotha
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PostPosted: 09:01 - 09 Jun 2019    Post subject: Reply with quote

GT200Fan79 wrote:
Fantastic to listen to a guy who knows his subject inside out.


agreed
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trevor saxe-coburg-gotha
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PostPosted: 09:05 - 09 Jun 2019    Post subject: Reply with quote

stinkwheel wrote:
My understanding is that there was a "figure" for maximum piston velocity that "everyone" knew about. Everyone that is, but Japanese piano makers.

They started making bikes that comprehensively blew that "Can't go any faster or the rings will weld themselves to the bore". Figure out of the water through pure ignorance and have never looked back.

In answer to the OP. An Indian 4 has a 2.75" bore and 3.75" stroke.

The Munch Mammut 2000 is exactly square. 86.0 x 86.0.


Cheers - and a good excuse to post a pic of that behemoth.


https://www.motorcyclespecs.co.za/Gallery%20%20A/Munch%202000%20%203.jpg

btw iirc the z1 was square too
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.Chris.
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PostPosted: 11:31 - 09 Jun 2019    Post subject: Reply with quote

The old Honda CB900F has an undersquare engine.
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Polarbear
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PostPosted: 12:01 - 09 Jun 2019    Post subject: Reply with quote

Not bikes, but the most powerful reciprocating engine in the world has a bore of 960mm and a stroke of 2500mm. Mean piston speed is 8.5m/s which considering the piston weighs 5.5 tonnes is some energy on the move.

I have no idea what bearing this has on your discussion, just thought you might find it interesting.

https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C
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Pete.
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PostPosted: 12:34 - 09 Jun 2019    Post subject: Reply with quote

.Chris. wrote:
The old Honda CB900F has an undersquare engine.


As did the early 750 which were either square or under, also the xj750 was (just about) under square though it's a triple not a four.
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Hong Kong Phooey
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PostPosted: 14:09 - 11 Jun 2019    Post subject: Reply with quote

Honda NC700 series
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trevor saxe-coburg-gotha
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PostPosted: 17:03 - 11 Jun 2019    Post subject: Reply with quote

twin
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Hong Kong Phooey
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PostPosted: 11:15 - 13 Jun 2019    Post subject: Reply with quote

...welded together?! Embarassed
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c_dug
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PostPosted: 13:20 - 13 Jun 2019    Post subject: Reply with quote

Hong Kong Phooey wrote:
...welded together?! Embarassed


So, Honda Jazz?
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trevor saxe-coburg-gotha
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PostPosted: 17:11 - 13 Jun 2019    Post subject: Reply with quote

Well, according to one of the mags (Bike?) Honda are under way w/ R&D on an IL6, which will have a kind of caf racer vibe i.e. a cockpit faring etc.

I'm guessing it's a kind of 'reply' to Kawasaki's Z900 and also the H2 w/ that super charger.
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Snod Blatter
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PostPosted: 15:18 - 15 Jun 2019    Post subject: Reply with quote

The old BMW K100 (and K75) has a bore x stroke of 67x70mm and willingly revs to 8K, really coming to life past 6K. It's all down to tune (as ever).

EDIT: Some research reveals the K1200RS (last of the longitudinal Ks) has a bore x stroke of 70.5x75mm and redlines at 9K, that's some serious piston weight and speed!
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