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  1. #1
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    "New" 2-stroke tech

    Most of you have probably seen the prototype of the 2002 Honda CR250 by now and are probably asking all kinds of questions about the electronically controlled powervalves, and whatever else might be new to this bike. Well, here is some news: this technology has been around for quite a while. I just purchased a 1994 Honda NSR 250. For those of you who dont know about this machine, here are the details: It is a v-twin 2-stroke 250cc street bike that uses some pretty advanced tech that allows it to achieve nearly 65hp at the rear wheel, with no engine mods. The heart of the technology (as much as I understand it) is a computer that monitors engine RPM, speed, temperature, and throttle position which it uses to control the ignition timing, exhaust powervalves, and powerjet carb. This system was also designed to use a card (kind of like a credit card) as the key. In the racing scene, you can use different cards to "tune" your bike for different tracks (high RPM or low RPM powerband as you choose). So here is the question for the experts: If this technology has been proven since before 1994, why have we not seen this technology move to the dirtbike scene sooner?







  2. #2
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    Because of the dirt




  3. #3
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    To much wieght? too expensive?
    CRG




  4. #4
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    Servo controlled power valve

    I posted a similar question a while back (tried a search, but it's gone now). I found out that the Yamaha WR200 from the early 90s actually had an electronically controlled powervalve, although it probably wasn't as high tech as the one in the NSR or the new CR. I also heard that electronic powervalves weren't legal according to AMA rules. Don't know if the rules have been changed since. Otherwise, it doesn't make a whole lot of sense for Honda to use the technology on their MXers.

    Norm




  5. #5
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    My friend ( a.k.a. MTRHEAD ) told me a while back that Bob Hannah rode works Honda's back in '85 that had electronic / servo drive power valves in supercross and nationals. He also said that several PWC and snowmobile companies have had them in production for some time. He also mentioned the WR200.

    He's very excited about this new motor and seems to think it's a milestone for modern two stroke MX engines. Claiming that from what he's seen in the photos he can tell that it should make some big top end. And that the new case reed / power valve set up should allow them to also have a very wide powerband with a lot of tuneability.




  6. #6
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    I dont think weight can be that much of an issue, this stuff is pretty light in construction.

    I should also add that this particular engine (NSR250) used this same design from around 1989-1998. Then Honda quit selling them.




  7. #7
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    The last (Swedish) Husqvarna CR250 of 1987 had a servo/motor controlled powervalve.




  8. #8
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    Yamaha has been using exhasut tuneing in street bikes (YZFs) for a while and I read an artilce on Honda 01s I think 929 RR and the RC51 that use electroicly tuned air boxes and exhaust to frequency resonate or "ring" the the whole flow. They even changed the color of the airbox plastic to white cause they claim it matteres! I too wonder why MX seems to be so low tech. I think the overall cost of what people are willing to pay, how hammered the bikes get, seems to behoove the manufactures to keep the cost lower for the average non pro MX folks where as road bike raceing is no holds bared what ever it takes to go .2 MPH faster than the competetion. Where is direct fuel injection on 2 and 4 strokes? Where are these hydro electronic valves for 4 strokes? This stuff is out there but Cannondale seems like the only one trying to push the envalope. Maybe cause they have the most to gain and the most to loose if their bikes dont prevail at a competitive cost.

    P.S. I saw a moutain bike at the bike shop that had an electronic suspension valve button on the handel bar that let you lock out the shocks for going up hills or on pavement.




  9. #9
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    Dirt bike tech does seem to be lagging. Some snowmobiles have electronic suspensions that adjust 1000 times/second, exhaust gas sensors that adjust the ignition timing to suit the conditions, throttle position sensors, and electronic exhaust valves.

    We're talking some extreme conditions for sleds, albeit, no dirt. The prices aren't that outrageous either. The future for bikes is EXCITING!




  10. #10
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    true about sleds, but in other areas, steds have been lagging behind for years. Wasn't too many years ago that damping adjustment (clickers) became available on sleds, and it still isn't available on some models. Spring preload adjustments are more popular.

    I think dirt bikes have had damping adjustments since at least the early eighties.

    Some sleds still have round slide carbs...I don't think any "performance" bikes still have round slide carbs.

    Kawasaki already has tried throttle position sensors a few years ago, didn't seem to have much benefit, at least the way they applied it.

    The Bombardier "RAVE" valve system, now in production for maybe 10-15 years, is simpler than most dirt bike power valves, and seems to work well. Very few moving parts.




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