Kawasaki dropped a serious bombshell last weekend, just before the start of the third AMA Supercross in Anaheim. With a telling teaser, the brand announced nothing less than the return of the two-stroke. Worldwide, every soul with a supply of two-stroke oil in the garage did a happy dance. We went to see what Kawasaki had already registered in the patents applied for.
Before you get all worked up: Kawasaki is no longer going to use carburetors. That is not feasible to meet current emission standards, so injection was adopted. Kawasaki’s two-stroke engine will be quite revolutionary because it tries to eliminate the typical disadvantages of a two-stroke by integrating ………. four-stroke technology.
Kawasaki has already started registering a number of patents for the new lifting technology in 2020. The first applications still mention a four-cylinder two-stroke with a turbo, but it is clear that this has since been further developed into a better system. What we now know is that this two-stroke design will be radically different from what we have known from the past. Also know that Kawasaki has a lot of experience in building two-stroke diesels for shipbuilding. The technology used is very similar to that used in ship engines.
A two-stroke diesel marine engine from Kawasaki Heavy Industries.
As mentioned, fuel injection will be necessary to meet the emission standards. Furthermore, there will no longer be any transfer ports on the cylinder, but the cylinder head will contain valves, just like with a four-stroke, to fill the cylinder with air. Whether that air is pushed under pressure (by a turbo) above the piston is not yet known. By using valves (and a possible turbo) the combustion process can be much more controlled. It goes without saying that an ECU will be responsible for controlling all of this.
Conventional two-strokes have a number of disadvantages such as high fuel consumption, poor emissions and a tighter power band. With Kawasaki's design, the brand tries to eliminate the disadvantages of a two-stroke by integrating four-stroke technology such as valves for the supply of fresh air (whether or not under pressure) and the discharge of burnt gases to the exhaust.
A patent application from 2020
Driven mass
Because injection is chosen, the transfer ports are eliminated, which means that there is no crankshaft lubrication either. This would mean that from now on, just like with a four-stroke, it would have to run in an oil bath. In addition, the camshaft also has to be lubricated, so an oil pump will also be needed. An oil bath with an oil pump present, together with the components in the cylinder head, take away power because they are part of the so-called driven mass. Perhaps Kawasaki has figured everything out in such a way that the loss of power does not outweigh the gain in power.
It also means that the mixture lubrication (automatic or not) can be adjusted, whereby a ratio of 1 liter of two-stroke oil to 100 liters of petrol becomes perfectly possible. It would certainly benefit the emissions of this type of two-stroke engine.
It may just be a coincidence, but it seems that Kawasaki have adapted their current frames to the arrival of the two-stroke. Since last year, the current KX250 and KX450 have a raised frame split at the front, which makes more room for a two-stroke exhaust. Just saying.
Kawasaki has at least listened to the sighs of its fans because the two-stroke has never been as popular as it is now. That their new two-strokes can be offered cheaper than the current four-strokes seems like a utopia to us because with what we know now, the engine will have a lot of extra technology on board and that comes with a price tag.
An alternative to electric motors?
Even though the timing of the announcement seems strange, given the current problems with global warming and increasingly strict emission standards, the fact is that the Japanese brand has to come to the market with a strong concept to convince everyone of the benefits of their new technology. Perhaps the timing of the announcement is a real success because the introduction of electric motocross bikes is meeting with a lot of resistance. For the non-believers of electro-motocross, the new Kawa could offer a solution, provided that the technology is environmentally friendly and does not make too much noise. Here too, the two-stroke has an advantage because the sound carries less far than with a four-stroke.
The last KX250 with a two-stroke engine dates back to 2007.
By implementing this new technology, the brand could also gain a foothold in Enduro. In that sport, the Austrians are the ones calling the shots because they can meet the current emission standards and that could also be the case for Kawasaki. So not much is known yet about what Kawasaki will come up with, but they have already made a very large audience happy with the news. It is not known when the technology will be offered for sale, but it will take a few years before the first new 'ring-ding-ding's' of the brand are in the shops.
Photos: Kawasaki in KHI
Tekst: Danny Hermans
