JJ2S X4 500 - 4 Cylinder 2 Stroke Concept Motorcycle
March 20th, 2008 by Paul Crowe - "The Kneeslider"
Motorcycle design often revolves around the engine. The size, shape, number of cylinders and configuration play a large part in much of what follows. What if you had an X4? 4 cylinders in an X configuration open up new design possibilities and that is exactly what we have here, not only that, it appears to be a 500cc 2 stroke! This is the JJ2S X4 500 by JJS Design. They have developed and patented a new engine and designed a motorcycle around it.
JJS Design is a Polish company and unfortunately my translating abilities here are not so good, so I can’t fill you in on many details but the design looks extremely impressive, both the motorcycle design itself and, of course, the X4 2 stroke engine.
I will try to get a translation of some of the information, any of our Polish readers care to lend a hand?
Thanks for the tip, Brian!
Lots of images below:
Link: JJS Design
Posted in Motorcycle Builders, Motorcycle Design, Motorcycle Technology
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26 Responses to “JJ2S X4 500 - 4 Cylinder 2 Stroke Concept Motorcycle”
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March 20th, 2008 at 10:02 am
I speak Polish, though it’s more conversational than technical. On the other hand, I am an engineer. I’ll try and provide a translation over the course of the weekend.
March 20th, 2008 at 11:30 am
I have an echo chainsaw with two opposed cylinders that share a common crankcase area. This two stroke looks to have separate crakecase areas for each cylinder. Must get pretty complex keeping the crank transfer areas apart but common.
March 20th, 2008 at 11:35 am
Great looking model, what are they going to do about the expansion chambers, this looks as though it uses exhaust off a four stroke. Also looks a little top heavy, given the amount of mass above the counter shaft location. Best of luck, cool looking project.
March 20th, 2008 at 11:55 am
The exhaust seems unresolved in this concept. Four expansion chambers large enough to accommodate 125cc combustion chambers seems to be overlooked.
March 20th, 2008 at 12:09 pm
This is actually a 3D render. All of these images. As far as I can tell there is no physical prototype - at least not in this bunch of images. I am a 3D artist by trade, and there are many signs that this is a render. Maybe the concept is cool, but I doubt there is a real prototype.
March 20th, 2008 at 3:30 pm
an X-4 two stroke could share a single crankcase as long as the pistons all travel towards the crank center at the same time. That would tend to suggest a crank with four throws and the necessary cylinder offsets.
The four separate carbs and no off-set do suggest four separate crank shafts. Maybe they are all gear driven to a central counter shaft. If so it’s not so bad. Square-four kawasakis had twin cranks geared together
Regardless, this design should have nearly perfect primary and secondary balance.
The velocity stacks, lack of air box, and megaphone exhaust all tell me this design is best suited to constant high RPM running.
Very nice rendering, should be fun to build a prototype.
-todd
March 20th, 2008 at 3:35 pm
I need to clarify that the no off-set X-4 would have four cranks in four separate, sealed crank cases. That’s 8 seals.
It would have been interesting to have the transmission in the center of the crank cases…
-todd
March 20th, 2008 at 4:27 pm
It looks to be a direct injection system that also uses reed valves to deliver fuel through the head, not from transfer ports from the crankcase. I am guessing this is how they manage to have such a compact, shared, crankcase. I also think that when you employ direct injection this way, you do not have the same issues of timing overlap with intake and exhaust ports, so you do not depend on the same type of tuned exhaust as a regular two-stroke. It is kind of like a four-stroke two stroke. Then again, I don’t read Polish and could be way off…
March 20th, 2008 at 5:18 pm
I fallen in love - thats the best looking bike I have seen since they first brought out the Ducati Monster
March 20th, 2008 at 7:33 pm
Haven’t you guys ever heard of a radial engine? I think that’s all this is, except it’s a 2 stroke, which would allow an even number of cylinders. 4 stroke radial aircraft engines require uneven cylinders (3,5,7,9,etc) to balance the firing order.
And the single crank is totally doable in this concept, just like radial aircraft cranks, where the connecting rods all meet in a central hub.
And I think it’s funny, these renderings are good enough that a few people thought it was a real bike!
March 20th, 2008 at 7:44 pm
Without a lower end squish happening there’s no way to make the charge hop into the combustion chamber, reed valves or no. The exhaust ports and the intakes look to be on the same plane. Coursion seem to be the only element usable. If the pistons go in and out in unison, why not one big carb in the center.
March 20th, 2008 at 7:48 pm
Hardly a new idea. Henry ford was experimenting with x shape car engines years ago but was never able to get them working well enough for production
March 20th, 2008 at 7:53 pm
Oh ya, Make that coercion…
March 20th, 2008 at 8:48 pm
So this is a four-cylinder radial, in other words. Or could be, anyway :-p
I smell the bike in the next X-Men spinoff :-p
cl
March 20th, 2008 at 11:45 pm
There are sooo many techno geeks on this site, and I mean that in the most complimentary way possible! Every time some new/forward thinking/outside the box design shows up, I can count on at least three or four uber brained technophiles to weigh in and send me into a frenzy of web searching which inevitably leaves me frustrated and, more often than not, actually knowing LESS than when I started.
Thanks a lot.
Rant over. I’m going to watch Robot Chicken and have a beer. Oh yeah, thats a wicked cool bike, rendered or not.
(It’s been said before and I’ll say it again.. This hands down the best motorcycle site out there) Thanks Kneeslider
March 20th, 2008 at 11:59 pm
I’m not Polish literate, but I can read drawings.
It sure looks to me like a sleeve valved engine.
More here to go by:
http://www.jjsdesign.net/jj2s/patent.html
There’s a lot that can be figured out by clicking around that site and browsing the illustrations.
The crankcases aren’t pressurized to charge the cylinders. The opposing pistons seem to be connected to each other - the crank operates with an eccentric.
Another drawing - there are LOTS of them:
http://konstrukcjeinzynierskie.pl/0004_schemat_jj2s.gif
Which came from:
http://konstrukcjeinzynierskie.pl/0004_schemat_jj2s.gif
In addition to more pictures, page 51 has the engine cycles illustrated:
http://www.konstrukcjeinzynierskie.pl/PiKI_2(2)2007_website_LQ.pdf
Note the balance tube between the crankcase and the top of the piston/sleeve/? chamber. The cases have nothing to do with charging the cylinder.
I’ve seen these referred to as stepped piston 2 strokes….
Here’s a stepped piston 2 stroke:
http://users.breathe.com/prhooper/opads.htm
March 21st, 2008 at 11:48 am
Mechanically this engine would not be able to run at high rpm if you look at the very elaborate and heavy piston/sleeve combo design. You’d have some very high stresses on crank/rods, compared to a conventional two-stroke.
And, yeah, expansionchambers are included under “the bare essentials”.
Pretty cool rendering, cool :o)
March 22nd, 2008 at 4:56 am
Anyone else seeing just how top-heavy this engine will be?
March 22nd, 2008 at 3:19 pm
Really nice concept and i would love to give it a try to see what it feels like. But i doubt it would be a performance engine in any way. The gearing system, assuming they use what rohorn suggested(by the way are two of the opposing cylinders offset? or the rods?), looks overly complex (the output comes out the left side of the engine and is then routed under the engine to come out the right hand side) and very heavy for the size of the bike.
March 22nd, 2008 at 5:10 pm
It is very cool but looks a long way from production. I LOVE two stroke road bikes, but it looks like the “concept” rendering of the RD500 which was in MCN and Performance Bikes is closer to production!
Can anyone explain to this idiot why all this fuel injection technology can’t be adapted to a two stroke engine? One of the posts above alludes to it, but my very limited understanding is that in a conventional two stroke you kind of have to have the inlets and exhausts open at the same time, and some of the unburnt charge “escapes” at certain revs, leading to the issues with emissions. given the nanosecond control of fuel charge and the myriad electronic monitoring/controls available, why can’t I have my RG500Gamma (got offered one for $8k NZD the other day… had to pass) but updated for 2008?
And sorry in advance for being a technical ignoramus: To misquote Leonard McCoy again “Dammit Jim, I’m a lawyer not an engineer”.
March 22nd, 2008 at 9:06 pm
There are plenty of fuel injected 2-strokes in snowmobiles, PWCs, outboard motors, etc…..
March 23rd, 2008 at 12:18 am
Tim… I’ve got 8 grand. Was the RD anywhere near Christchurch?
March 24th, 2008 at 7:19 am
It’s a well known design in Poland, but still controversial. The constructor has to deal with lack of money and other problems, but he was already able to forge a running small scale model of the engine. We are going to put some info about this news on our webpage with a request for help with translating. We hope that somebody will be able to help. Good work after all.
March 25th, 2008 at 4:17 am
Here you have an animation of that engine. For those who do not know how does it look:)
http://www.jjsdesign.net/jj2s/video/jj2s05.avi
March 29th, 2008 at 3:37 am
Hello,
I am from Poland and I’ll try to explain how the engine works. It is a bit complex. Basically it works as a 2 stroke - each cylinder delivers power once a turn of crankshaft. However the crankshaft and the crankcase are closed and lubricated normally with dry sump system as in 4 stroke engines. The X4 engine is combining the efficiency of a 2stroke engine and it has reduced pollution.
Furthermore the engine has less vibration on high rpm than in lower rpm. It is using a special crank design.
The prototype of this engine is actually working - they have build a small, one cylinder 5cc engine to prove the design is good, and the small engine is fully operative. Now the are working on a 125cc version, and after that they will try to build the X4, 500cc, ~100 HP version. It will be equipped with direct fuel injection system.
The motorcycle itself is estimated to cost about 20.000 - 25.000 $ .
March 29th, 2008 at 3:47 am
I would like to add something. The basic design of the engine is similar to a big, marine, diesel engines. Those are also two stroke but they are lubricated in a normal way, as in 4 stroke engines.
The main difference is that those big ship engines need to be supercharged to work. And the X4 engine has a special self-charging system. The air and the fuel mixture are pre-charged there and when the piston opens the port it rushes into the combustion chamber and the exhaust gases leave. Then the mixture is compressed, ignited by a spark plug etc.
To fully understand how it works you need to visit the website.