just for the hell of it


14 replies to this topic
  • timmy.g

Posted January 29, 2005 - 04:27 PM

#1

you guys with these highstrung fourstrokes. Whey do think it has taken all these years for the makers to come up with these lightweight hirevving bikes??. Seems like they've had the techn. for lots of years. I guess maybe that yz400f was maybe the first one in '98 or so. Just wanting some thoughts on this??

  • grayracer513

Posted January 29, 2005 - 05:53 PM

#2

The reality was in the late seventies, that four strokes could not compete any longer with two stroke MX bikes of the same displacement. This is still true to a degree today, especially outdoors, but not as much as it was then. Anyway, various organizing bodies became concerned that pollution policy would one day eliminate two-strokes and, if four stroke development ceased at then current levels, there might be no MX if that were to happen. So, it was decided to allow the four strokes a displacement handicap. Yamaha was on this like seagulls at a dump in no time, and immediately came up with the YZ400. They won the AMA 250 class national championship with it in 1998, and followed that with the introduction of the YZ250F. It sort of went from there after that.

Now, it's got to the point that I hear people crying foul when somebody runs a YZ250F in the 250 class on some tighter tracks, and the little blue bike is putting out power at the same levels the 2 strokes were in 1986. Who knows where it's going to end up? :cry:

  • timmy.g

Posted January 30, 2005 - 10:17 AM

#3

That seems a very good comparison. But i hav never seen a 250f in the 250 class??:cry:

" Yamaha was on this like seagulls at a dump in no time",

Now, it's got to the point that I hear people crying foul when somebody runs a YZ250F in the 250 class on some tighter tracks, and the little blue bike is putting out power at the same levels the 2 strokes were in 1986. Who knows where it's going to end up? :cry:



  • sirthumpalot

Posted January 30, 2005 - 10:59 AM

#4

4-strokes have always produced nice power, and for quite some years we've been able to produce very powerful 4-strokes. But the technology had not existed to build a 4-stroke that was both powerful and light enough to compete with 2-strokes at an AFFORDALBE PRICE (key words). Over the years as we MX types kept the 2-stroke development ball rolling, our superbike bretheren drove the [high performance] 4-stroke motorcycle engine development. Note that both groups had the same basic goals; more reliable power, less weight and an affordable price. One day it was realized that by borrowing a bit of technology from our superbike (and maybe F1, etc..) groups that we could in fact produce a 4-stroke MX bike that was all things; at least as powerful as 2-strokes in the same class, reasonably reliable, light enough to be competitive and at a price that the average MX rider could afford. Someone at Yamaha with enough pull to influence the R&D money flow believed in the project and enough funding was provided to combine these technologies to begin development of a new 4-stroke MX bike. Insert some time for R&D and presto the YZF400 works bike was born. While the Yamaha marketing department (race team) was busy parading the works bike around the world showing that Yamaha has the technology to produce a 4-stroke that could indeed compete with 2-strokes in MX racing, the Yamaha engineers were hard at work engineering a version of this new 4-stroke MX bike that could be mass produced. A short time later the production YZF400 was born. I'm sure Honda, Suzuki, etc.. were all paying very close attention to see what happened next. As those bikes began to sell, and it became apparent to the manufacturers that 4-stroke MX bikes were warmly received by the MX crowd (read: big proffits to be had here), in went more R&D money, and out popped newly refined models and models from other manufacturers. Time has proven this to be a very profitable market, and it's been down hill from there. At least this is how I see it. :cry: :cry: :cry:

  • grayracer513

Posted January 30, 2005 - 11:21 AM

#5

... i hav never seen a 250f in the 250 class??:cry:

I have, and you should hear people scream when they win. They claim the light weight is an unfair advantage, even though the bike is above the minimum weight for a 250. Consider the irony of the fact that the 250F is 5 pounds lighter than a YZ250 with an aluminum frame, even with its 2 cams and all.

  • Satch0922

Posted January 30, 2005 - 11:29 AM

#6

your right! I never even thought of that... makes my head spin.....250 thump lighter than a 250 smoker......VERY INTERESTING

  • 642MX

Posted January 30, 2005 - 01:37 PM

#7

That seems a very good comparison. But i hav never seen a 250f in the 250 class??:cry:

Come to southern Indiana, they allow it at almost every track. I haven't heard too much crying over it though. Remember 90% rider 10% bike.:cry:

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  • Frostbite

Posted January 31, 2005 - 01:16 PM

#8

[font=Times New Roman][size=3]Honda was playing with high output 4 stroke GP bikes years and years ago. I can’t remember the exact details but they built a super high revving 125cc 6 cylinder oval piston bike with 16(I think) valves per cylinder. The valves were tiny, the size of pencil erasers. 96 valves, must’ve been fun adjusting the clearances on that puppy.[/size][/font]

  • grayracer513

Posted January 31, 2005 - 02:00 PM

#9

[font=Times New Roman][size=3]Honda was playing with high output 4 stroke GP bikes years and years ago. I can’t remember the exact details but they built a super high revving 125cc 6 cylinder oval piston bike with 16(I think) valves per cylinder. The valves were tiny, the size of pencil erasers. 96 valves, must’ve been fun adjusting the clearances on that puppy.[/size][/font]

The Euro GP world produced some very exotic things. Moto Guzzi had a 500cc V8 (yes VEE EIGHT) that was the sweetest sounding thing you've ever heard. And, of course, Honda had several. The motorcycle that dominated the GP circuit for years was the 297cc six cylinder, 24 valve stretched out of a 250cc design to attack the 500 class, ridden by Mike Hailwood. It was untouchable.

The 125 was actually a 5 cylinder, 20 valve design. I believe the spark plugs had 6mm threads. The kicker was the redline: 22,500 RPM! It required custom fuel to run at that speed, and had to be kept above 7,000 rpm at all times to avoid severe pinging.

But that stuff was pure unobtainium, and building a suitable MX engine with that kind of technology was out of the question. A lot of the current, consumer accessible technology was first pioneered by the likes of Ducati, who began to realize that extreme high rpm was the only way to generate the power required to compete with two-strokes and big multis. This lead them to their experiments with valve gear designs and severely over-square engines (a bore equal to the stroke is called square. Over-square is when the bore is a larger dimension).

Like I said, what finally uncorked the modern MX thumper, apart from the improvements in production techniques and metallurgy that helped make it affordable, was the idea of granting a displacement handicap to the four-stroke. One wonders if Yamaha had anything to do with the politics of that, because it looks like they accomplished about 6 years of development on the YZ400F in about a year and a half.

  • Frostbite

Posted February 02, 2005 - 05:55 AM

#10

Technology uncorked a lot of things, including Mike the Bike, who is now Michelle.

  • Fastest1

Posted February 02, 2005 - 06:42 AM

#11

Though I agree that many people have built multi cylinder high revving bikes, Ducati was not the leader in technology. Just to have a high revving bike is not necessarily an advantage as witnessed by todays GP bikes. Bikes with a useable powerband and torque seem to allow a rider more versatility. Being able to apply throttle earlier upon exiting turns is what makes for quicker lap times. Time spent on the straightaways is much less than in corners. Case in point, Valentino Rossi's going to Yamaha and smoothing out the motor is what helped him win not more power or revs. 2 strokes will eventually be outpowered due to better burn of the available fuel and pneumatic/electric valve technology. Maybe even electromagnetic bearings that allow crankshafts to float with no contact. Camshafts will be eliminated for processors for valve opening. Just a question, since everyone praises big 2 smokes as they were supposed to be the most powerful, why are their lap times not faster? Their acceleration and peak hp might be higher, but the width of power is very limited making them very hard to ride. Nobody thought GP racing would be exciting or competitive with 4 strokes either, Wrong. If 2 smokes were truly better/faster, Indy and F1 would be running 2 smokes. Thank God for technology.

  • Frostbite

Posted February 02, 2005 - 09:04 AM

#12

Very true. I was racing a 600 Hurricane against RG 500 2 smokes which had a lot more power but on a tight track they were not serious competetion.
A great rider can still make it work though. Remember when Eddie Lawson stuffed a Kawi 750 triple 2 smoke into a flat track frame and won with it? Ah, the good ol' days.....

  • durtslinger

Posted February 02, 2005 - 09:17 AM

#13

you must not ride harescrambles.

250 class is 250 class- no matter how many strokes.

  • grayracer513

Posted February 02, 2005 - 09:45 AM

#14

Though I agree that many people have built multi cylinder high revving bikes, Ducati was not the leader in technology. Just to have a high revving bike is not necessarily an advantage as witnessed by todays GP bikes. Bikes with a useable powerband and torque seem to allow a rider more versatility. Being able to apply throttle earlier upon exiting turns is what makes for quicker lap times. Time spent on the straightaways is much less than in corners. Case in point, Valentino Rossi's going to Yamaha and smoothing out the motor is what helped him win not more power or revs. 2 strokes will eventually be outpowered due to better burn of the available fuel and pneumatic/electric valve technology. Maybe even electromagnetic bearings that allow crankshafts to float with no contact. Camshafts will be eliminated for processors for valve opening. Just a question, since everyone praises big 2 smokes as they were supposed to be the most powerful, why are their lap times not faster? Their acceleration and peak hp might be higher, but the width of power is very limited making them very hard to ride. Nobody thought GP racing would be exciting or competitive with 4 strokes either, Wrong. If 2 smokes were truly better/faster, Indy and F1 would be running 2 smokes. Thank God for technology.

Ducati was indeed not the leader in developing the current modern four-stroke, but they were certainly one of the leaders at that particular point in time. Their problem was that they don't have a 4 cylinder, and weren't going to make one, but they needed to be able to compete against them and the odd two-stroke as well. They were one of the first to move toward the radically oversquare engines that are so common in MX 4-strokes now, and who else ever produced a road bike with a desmodromic valve train? They were also an early experimenter with pneumatic valve "springs". Until Ducati started to make this effort, running a 1 liter v-twin at 11,000 rpm was unheard of. Certainly, they have not been as much on the overall cutting edge as the Japanese, but they have been a contributor.

Tractability is, as you say, a major consideration in road racing, just as it is in most other types of the sport. But what has done the most to kill off the big two-stroke are the rules that demand a production version be sold to the general public. How many 750cc 2-stroke road bikes are there? (There won't be any very soon, either). When Yamaha was campaining their TZ750 4cyl in the 70s, it was entirely untouchable at all but the very tightest courses in spite of its peaky nature. I venture that that same engine, with a few updates and in a modern chassis would not only dominate its own displacement class, but would give a GSX-R all it could stand.

As far as their use in car racing, there has always seemed to be a practical ceiling to the size a two-stroke can be made, and I don't recall having ever seen one larger than 1 liter that amounted to anything, except possibly an outboard powerhead.

  • RJB

Posted February 02, 2005 - 08:44 PM

#15

your right! I never even thought of that... makes my head spin.....250 thump lighter than a 250 smoker......VERY INTERESTING


rethinking that YZ250 smoker purchase now Satch? :cry:





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