The old Jawa name is now owned by Mahindra, along with BSA and Peugeot’s motorcycle brand. The first ground-up product from the reborn Jawa is this handsomely retro-styled 300cc four-stroke single. No word on whether it will ever be sold in Europe or North America, or how it will actually perform, but (other than a bit kludging around the radiator) it’s just smashing looking, in my book.
Last Call indicates the end of Hooniverse’s broadcast day. It’s meant to be an open forum for anyone and anything. Thread jacking is not only accepted, it’s encouraged.
Last Call: Jawa Doin'? Edition
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15 responses to “Last Call: Jawa Doin'? Edition”
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Q: If the Jawa is a 300cc single, why two exhaust pipes? A fake dual exhaust would be disappointing, much as it would be on a car. But yeah, that’s one stylin’ scooter.
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Probably for the same reason Honda’s 500, 600 and 650 singles have had since the late seventies.
A four valve head with the two exhaust ports kept separate from each other all the way out into the separate exhaust headers.
It makes a lot of sense from a thermodynamic loading point of view on a single cylinder engine, on multi-cylinder engines it can get too cramped to fit in all the pipes and there is a fabrication problem with the pipes as well, it’s hard to get the welds right on complex exhausts. Differential expansion and contraction rates with heat cycling tend to cause cracks.
But for a single, keeping the exhausts separate works well. All the way to the mufflers, like Jawa has done
https://rmsothebys-cache.azureedge.net/6/8/0/1/e/e/6801ee153f441db1a79222274648dcc5f914b275.jpg-
the “dual port” single goes all the way back to the 1920s for airflow and packaging reasons. To expand on Rover1’s Honda example, radial 4 valve heads as used on a variety or XL/XR engines give even more reason for dual pipes because the exhaust valves and their respective ports are widely separated so it makes sense to use separate runners although Honda used a 2 into 1 collector with a single muffler for weight and tuning reasons
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Awww… why are you all giving well-reasoned, factual answers?
Here I was – ready to claim that second pipe was just a verrrrry looooong inlet manifold…
..and you all jump in with your ‘facts’!
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Ah! See, this is why I hang out here. Most excellent info, thanks! I hadn’t considered that dual port could also apply to exhaust, and would make perfect sense in a 4-valve head.
Can you tell I don’t spend a lot of time around motorcycles? Working on that.-
It’s easy(?) to see why doubling the complexity of an exhaust system is best avoided by combining the exhaust flows from each valve into only one pipe instead of two, on multi-cylinder engines when we look at the complexity of the exhaust of a radial engine made from nine Honda XR 600 singles by Australian Russell Sutton. It’s already complex enough making the rest of the engine first anyway
https://i.blogs.es/c84acc/radial3/650_1200.jpg
https://i.pinimg.com/originals/c7/d6/9a/c7d69ab67de8553c02c0555409267b90.jpg
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J’We doin’ jus’ fine, thankyou.
https://www.sideshowtoy.com/wp-content/uploads/2015/06/star-wars-jawa-sixth-scale-set-thumb-100122.jpg -
Nope. This bike will not be seen on european roads.
Registration requirements for EU countries for new motorbikes since 2017 are:
Emission standard= Euro 4 (minimum).
Noise emission= 78 Decibel (maximum).
Brake system= anti-lock brakes (front and rear).
Servicing= On-Board-Diagnose (OBD II minimum).
In other words, there won’t be any new motorbikes from India/China or other 3rd world countries in Europe. This is even harder than anyhing Trump would impose on China.-
Actually, the engine has been designed to meet Euro specs. It will be appearing in Europe wearing different bodywork and a BSA badge in a year or two. The only certain required change from Indian Jawa spec would be a disc rear brake for full, 2-wheel ABS. You can see the ABS tooth wheel on the front wheel now.
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I speculate Mahindra is going after the Royal Enfield Bullett 350 market in India, since Enfield seems to be betting on their new twin cylinder 650 and 750
https://www.visordown.com/feature/reviews/first-ride/first-ride-2019-royal-enfield-650-twins-ridden
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It is a absolutely fantastic … except for that radiator. A shame it can’t be air cooled.
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Kind of agree from a looks stand point. But a good running 300 liquid cooled motor should be able to keep up on the highway. Which would be a big plus.
On the flip side i think I like how the headlight bucket holds the instrument cluster without killing the lines( at least from the view posted above.) -
It is very hard to meet emissions standards with aircooled engines. A very tight control needs to be kept on combustion chamber temperature and it is very hard to do that when the space that surrounds the chamber varies widely in temperature with airflow. Also, as Kevin Cameron pointed out in ‘Cycle’ magazine years ago, water weighs less than metal. A properly designed watercooled engine complete with radiator and water pump will weigh less than an air cooled engine of similar capacity and output, because it doesn’t need all that thermal mass of extra metal and cooling fins, or in automotive use, cooling fans as well. Less weight is better for everything.
And by keeping the valve seats cooler, watercooled engines are more reliable and longer lived and meet emissions controls longer, (which is actually part of the emissions legislation too).
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Quite nice. I didn’t know Czechs sold the brand. New owners really should make that sidecar, and as true to original as bike is to Jawa 250 (type 353):
https://uploads.disquscdn.com/images/2940f0a7c22640e7bc903cf89304121c6cd3f5ffc129a0b5b1d372465792ac5e.jpg
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