aargee

#1 - I was amazed to see the bore & stroke of the middle weights the same for the top 4 brands of Japanese motorcycles
2012 Yamaha YZF-R6 Specifications, specs
2012 CBR600RR Specifications - Honda Powersports
2012 Ninja® ZX?-6R Supersport - Kawasaki.com
Suzuki GSX R 600

How come the bore & stroke are the same 67.0 x 42.5mm for all the four manufacturers? Is it a coincidence or something that has matured over time or something standards on 599cc engines? Yes, there're differences in compression ratios, but still, almost everything else are the same. Any specific reason?

#2 - Also to notice that Suzuki has official SBK (GSX 750) while the other 3 manufacturers have ignored; to me it sounded like a bare minimum passport to enter official SBK category, so, why do the competitors miss it? Probably Triumph Daytona & Ducati 848 Evo qualifies from my knowledge, but, why do the other 3 manufacturer miss it? Isn't that a lost opportunity?

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sunilg

Query approved.

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satyenpoojary

Interesting.
I think its an evolution.. though the Jap4s are known to share vital R&D know how with each other, especially in times of crisis.
It wouldnt be surprising to know that the same foundry perhaps make the block sets for all these 4 manufacturers.

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L.P.

Though I can't Argue with Argee on any of his question, This one's has just left me unanswerable.

And I also am thinking on the same platform as Satyen, It may be just due to a Evolution, process at the initial stages, that it was designed to be at that spec, or probably, the kind of output they want as a result is best suited at this frame of specs only

Rest, NO IDEA, Sir Ji.


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Harmeet

Just like they agreed for 300km/hr top speed for litre bikes, they have now agreed for this boreXstroke size for 600's...


On a serious note. I dont think it is coincidence. This might be the perfect oversquare configuration for a 600 cc inline 4cyl engine. Hence has been adapted by all jap manufacturers.

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aargee

Pls...can you define what is perfect oversquare engine? Because Wiki says perfect oversquare engine is when bore matches stroke - Stroke ratio - Wikipedia, the free encyclopedia (1:1) and these work to something 1.57:1

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antz.bin

@RG Let him explain what he meant. You got yours wrong

Source: Stroke ratio (Square Engines) - Wikipedia, the free encyclopedia

examples of square engines would be Honda Unicorn, Yamaha FZ and Bugatti Veyron

P.S.: I googled 'Perfect Oversquare Engine'. No relevant articles found.

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nitrosatya

Perhaps they bought over the competitor's bikes to study and reverse engineer them. So to be on par with others, why not have the same dimensions?

Harmeet

Sure.
When the bore size (piston dia) is more than the stroke length the engine is said to have an oversquare configuration,
As mentioned above, all 600's have 67x42.5mm config where Bore=67mm and stroke=42.5mm.
Bore>Stroke.

Perfect oversquare might mean 1:1 bore/stroke ration but that does not mean than it will produce max power.
I mean perfect with respect to cylinder height, weight, block width, torque and power production and many other factors that might be considered for choosing a piston size.

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Kayos_inc

My two cents: if you read the reviews of these bikes old and new, you will find ; at most of the time the CBR is liked for street credibility, the R6 for track, the GSX for torque,Kawasaki for Raw power.Although they might have the same cylinder dimensions but their valve sizes, valve angles, manifold lengths,injectors, and everything else differs, and that makes the most of the difference to the bike's character coupled with different frames and suspensions.