The Future Of Two Strokes And Your Dirt Bike(cool article)

[seth399]

http://www.dirt-bike-tips-and-pics.c...o-strokes.html

I have read so much to do with Honda over the years that pisses me off and this adds to that

...He did not begin with the long-stroke CR250, but with half of Honda's NSR500V. This was a case-reed road-racing engine with a square bore-stroke ratio - like the McGrath generation YZ250s. Honda said that it made "135-plus horsepower" at 10,500 rpm; about 68-hp for a 250.

If ten-five makes it sound like all the power was on the top end, one rider called it a "torque monster" and said the power was "similar to an open-class motocrosser". This engine was introduced at the first 500 GP, 1996. I have given these details because there has been, at least, the suggestion that the long-stroke 250 two-stroke had reached some sort of a technological limit (at less than 50-hp) and that the 450 four-stroke was some sort of a 'solution' to this 'problem'. In 2005, MotoVerde magazine (Spain) dyno tested the CRF450 and the RMZ450 and got 56-hp and 55.2-hp, respectively.
There was a rumor that the NSR500V might be turned into a killer street bike. Of course, that never happened. Instead, Ishibashi was sent off to design Civic door latches, or whatever...

[seth399]

About now, someone should be asking: "If Honda knew how to make two-strokes that are cleaner and more economical than their four-strokes, that do not require any new technology, and that could win endurance races, why didn't they produce them?"

Back in 1984, Steve Anderson (then Technical Editor of Cycle World Magazine) went to Japan for a VIP tour of Honda's (then) new racing R&D facility. There, Takeo Fukui, Design Director, "...made it clear that Honda views itself as a four-stroke company that will not be satisfied until it wins all of its championships with four-strokes." Simply put, the four-stroke engine has been company policy; in fact, it has been more of a religion. Anderson saw, "...shelf after shelf of oval pistons..." and was told that engines were running "...with at least eight valves per cylinder..." and turbo charging. We haven't heard anything about oval pistons in a long time because, after spending umpteen millions of dollars, somebody saw that it was a really stupid idea. It was a way of getting around the racing rules. Four-strokes couldn't win within the rules, so Honda had to find some way to beat the two-strokes and/or the rules. The trouble was, no matter what the shape of the pistons, or how many valves they could stuff in, or how many rpm they could get out of them, the two-strokes kept getting faster and the four-strokes weren't even able to keep pace. In 1995, Mick Doohan was asked how much power his NSR500 two-stroke made: "I can't tell you that, but I can tell you that if Honda produced a one-liter motor it would make upwards of 400 horsepower."

[Kurlon]

KTM, Aprilia and others have improved two strokes to the point that they can meet euro-3 emissions, but US law just bans the tech instead so we'll never see them on the street. Stupid way of doing things.

[Tricky Mike]

interesting read... I didn't know that BMW G 450 X had a crank-mounted clutch.

[seth399]

interesting read... I didn't know that BMW G 450 X had a crank-mounted clutch.

ya seriously, pretty neat

[Tricky Mike]

Cool that KTM is still in the fight

LINK

“At KTM the two-stroke will continue to remain an integral part of the future model planning. We have already recognised new topics and initiated the development of even more powerful, quieter and above all less polluting two-stroke sports models within the framework of a specific project grouping.”

[Pittenger5]

How do you ride two strokes on the street? As far as fillups go? Do all of them need pre-mix to run?

[Paul_E_D]

newer tech is oil injected. You don't pre-mix, you fill a tank.

[Tricky Mike]

yup, oil injected, fuel injected. Cool stuff.

[Pittenger5]

So how often do you have to add oil? Or does it not burn off?

[Tricky Mike]

So how often do you have to add oil? Or does it not burn off?

From the article:
"When just the right amount of oil - not too much or too little - is metered to all the parts that require lubrication, the amount of oil consumed is surprisingly small. The last Suzuki two-stroke road bike that I tested went 1700 miles on a quart to oil. That was a 550-cc triple, in late 1977. "

[seth399]

not really sure, depends on how much they hold. I guess some new snowmobiles work like that

[Kurlon]

I'm still waiting for an Italjet to use it's first tankful of oil... multiple multiple multiple tanks of gas, still plenty of oil... Fun lil 50cc scoot that'll do 60+

[Tricky Mike]

Looks like Lotus is in the mix too:

http://reviews.cnet.com/8301-13746_7...g=2547-1_3-0-5

[Doc]

newer tech is oil injected. You don't pre-mix, you fill a tank.

Even my YSR is oil injected. As was the 2 Stroke Yamaha I Had. (RD350?)