2-stroke engine powered bikes are officially dead. Aprilia RS125 and Derbi GPR 125 are among latest “victims”. The only road motorcycle (that I can remember at the moment) that still uses 2-stroke engine is Cagiva Mito, but I guess this will have to change soon as well. All 2-stroke engines that might still be in production are going to be replaced with modern 4-strokers. The only exceptions are 50cc engines, but you can find a lot four stroke engines among these tiny ones as well.
Two strokers failed to follow modern anti pollution standard. This is the main reason why this happens. Other faults would be high fuel consumption, requirement of oil addition in fuel (which is partly fixed by automatic mixing devices, but good oil remained expensive), and I would say durability was also often under suspicion.
They also had some positives sides, such as much more power from the same volume comparing to 4 strokers (double rate of power strokes), very simple design (no valves, no camshafts) - which make them light weight, and also cheaper to produce and easier to maintain.
Few years ago I was reading about new kind of 2-strokers, that will bring them back to the scene, but that never happened. Maybe the development or production of these turned to be too expensive, I don't know.
In the last few years I read several comparison tests between various 125cc bikes, with mixed two-strokers and four-strokers. I really didn’t like those tests. Comparing such bikes with different engine types is illogical and unfair. These two types of engines are radically different, each with its own advantages and disadvantages, but most important nonsense was huge horse power difference. 12-15 Hp (about 9-11 Kw) was typical for 4-strokers while 2 strokers normally double those values.
Some of you would say: “yes, but they’ve been using restricted 2-stroke version, with similar power”… but that also does not make them equal. 2-stroke powered bikes were designed to handle much more power and speed, so all the parts were at higher spec level - frame, brakes, tyres... so the comparisons were illogical in any case.
Soon, among 125s, we’ll have Cagiva Mito in the class of its own, and all the others are now 4-strokers, with the newcomer – Aprilia RS4. I was hoping Aprilia would release it this year, but most probably it will be ready for 2012. Knowing Aprilia, and especially after seeing the photos of it, I think all the others will be in trouble. That's why I like Aprilia - they make every motorcycle, even the smallest ones, with the same quality and attention to details. Probably the only disadvantage of Aprilia RS4 will be the price. But we shall wait and see.
There are more things that will change because of 4-strokers total take over. I believe one of them is reviving of 250cc class. Why? Well, the total disappearance of 125cc 2 strokers is creating the gap, since new 4-strokers typically produce about 10-15 Hp. The result is total shortage in road motorcycles with power between 20 – 40 Hp (15-30 Kw).
I believe that this will lead4 to increased popularity of 250cc bikes. Honda joined Kawasaki and Hyosung at this piece of market with brand new CBR 250R, and I expect there will be more newcomers in this class, from Yamaha, Suzuki, maybe Aprilia. There is also rumor that KTM is preparing 250cc sporty naked bike. Kawasaki will be under great pressure in order to save the throne in this class, so it is possible that Ninja 250 will be slightly updated within next 2 years.
Among larger bikes 2 strokers have disappeared long time ago, so there’s nothing to say there.
Recent economy crisis that still keeps pushing down economy in most countries is one more reason why I believe that 125s, and even more 250s will become more popular. They are cheaper to buy and maintain, they are easy on fuel and easy to live with. They are not rockets, but are practical and still can be fun.
In my opinion there is also total lack of bikes 250-600cc, which is a shame.
Most of people actually do not need more than 70 ponies, but manufacturers today do not give us much choice. It's either 15-30 Hp or you can go to 100+. There is almost nothing in between.
I hope to see more of new fine125cc bikes – they’re good for learning, let’s attract more people to ride with us.
250cc, 400cc, 500cc ... these could work for most of people.
I believe, with solid quality and accessible price, factories can make a good job with some of these. I think it’s about time. Those who quickly involve with these almost forgotten small-medium classes will have a real advantage. And I think they should all really try and push them - worldwide! The buyers are waiting, I’m sure.