Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: 2stroker on June 17, 2010, 03:52:51 AM
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just wanted to post this article about making a yz250 competitive in the 450 class from motocross action. Hats off to them there mag seems to have more two strokes in it every issue
http://motocrossactionmag.com/Main/News/WE-BUILD-AN-LA-SLEEVE-YAMAHA-YZ270--6890.aspx (http://motocrossactionmag.com/Main/News/WE-BUILD-AN-LA-SLEEVE-YAMAHA-YZ270--6890.aspx)
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Cool article and good looking bike.
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Didn't Ohlins make a 360 cc kit for the YZ250 at one time?
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Not bad for modern media, wonder when the 330 kit will available?
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Didn't Ohlins make a 360 cc kit for the YZ250 at one time?
Not sure if it was Ohlins, but yes... Hung out with Mickey Dymond back in 1989 at DeAnza when he was riding one. I think they even ran them in the 500 Nats at one point.
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Motocross action did the same thing with a YZ285 in July 2007.
I have it in pdf if someone can tell me how to post it on here. Can't get it to work :(
Or just look it up on the web.
Has anyone here had experience with big bore kits ?
Foward Motion/Athena/Kustom Kraft do kits. Which ones are the best ?
Kustom Kraft do a 301cc kit for KX's. I might do my mates when it is due for a piston.
He might be able to keep up then :D ;D
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Bah! Broader, more usable power, no real increase on top. This is more of the same pablum I've been seeing for the past few years, makes me want to puke. Spend a lot of your hard earned dough on a bike to make it "more" competitive with the 450 thumpers. It Narrows the gap a bit, so to speak. Well, so to speak, that is totally unacceptable! If I'm going to hop up a 250 to compete with a 450 thumper, it is not mission accomplished until I can pull that 450 through the gears, period! Think about it a moment. The Project 250 YZ would smoke this bike with the LA sleeve kit. It would simply run off and leave it, and it's still a genuine 250. No way would I spend hard earned money on anything that would not enable me to go head to head with a 450 and at the very least, be equal with it through the gears, and even that is too little.
If folks think that this kit is a great idea though, so be it. To me, it's a total cop out. A 250 2stroke can be built to out accelerate a 450 4stroke, and if it's not doing that, it's not being built right. Personally, I don't care much for artificial track riding so I'd likely just get a KX 500 to start with and smoke the silly 450s out in the desert. Smoke them in drag races, up seemingly impossible sand dunes, and just about anywhere else. You want real horsepower and torque, compared to a KX or CR 500, the 450 thumpers are a joke. In the desert, we don't have to play by the silly AMA rules. Nevertheless, I realize for motocrossers, the rules are a fact of life. Therefore, why waste money on a hop up that still will leave you eating 450 roost? I could understand this if that was the best that could be done, but it's not. I feel this is a "politically correct" cop-out by MXA. They know how to make a 250 2stroke hop-up that will beat a 450 thumper, but they are not about to do this. I assume they are afraid to. Project 250's bike is merely one example demonstrating one way this can be done, but it's not like it takes a miracle or something. They want us thinking that the best we can do is get a little closer to the performance levels of a 450 4stroke, but never actually out-perform one, heaven forbid! Don't let them get you to thinking this way. If we do, we've lost the battle already.
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If there's anything to be leaned from those 4 strokes is that having a explosive hard hitting powerband is not realy necessary to turn out fast lap times.
Corner speed and traction is were it's at, not dragracing from turn to turn
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Ah, well, Scotty, then there is no problem. The 250 2stroke already does that, so the 450s should be losing. Don't seem to me to be the case though. If you've got two machines that both turn reasonably well, the one that gets from point A to point B quicker, will generally be the winner. In this thread here,
http://twostrokemotocross.com/forum/index.php?topic=768.0 (http://twostrokemotocross.com/forum/index.php?topic=768.0)
which bike got to the first turn? It seems to me that this shouldn't have happened. He had too much power and for a 2stroke, that means he can't get enough traction. So how did he do it? You start with getting the amount of power you need, "THEN" focus on making sure it gets to the ground. If not, why are the 450s beating the 250 2strokes most of the time? Don't kid yourself, accelerating is very important here.
I'm not willing to accept that twostrokes must be less powerful than 4strokes or they won't be able to get the traction needed to accelerate with them. The very thing I hear next is that we must have a bit less power to get traction, but the 4 stroke can get traction with more power. Hmm. What happens then? We get beat from turn to turn and at the start. So then, either way we are told we must passively accept 4strokes out-accelerating us, either because we don't have enough power to compete, or because we have too much. Best we can hope for is a tight track with lots of turns and maybe, just maybe, we can beat them utilizing our light weight and superior turning ability.
Sorry, I don't swallow that line of thinking. Think that way and things will continue as they are and the twostroke will become extinct. This is giving the thumpers an automatic built in advantage. Again, where does that leave us?
1. If I give my 250 enough power to actually out-accelerate a 450 on pavement, I will not be able to use that power, because in the dirt, I will just spin out where he is hooking up.
2. If I simply broaden and smooth out the powerband, I now get good traction and am ready for the race. Ah, but wait, the 450 gets good traction too, has a broader powerband and considerably more hp and torque, and is smoking me once again.
Conclusion: We must invariably accept a back set against 450 4strokes when it comes to acceleration and simply pray we can take the corners so much faster than them, that it will make up the difference and allow us to win.
Again, 2strokes can already out-corner 450 4strokes. The KTM 250SX has a very smooth powerband, why can't it usually turn faster lap times than a KTM 450SX? It just doesn't have quite enough power. You see, the 450 turns very well also. It's not quite as nimble or quick through the turns, nor can it change lines instantly like the 250, yet it will generally get better lap times on today's tracks because it has more power and better acceleration. I'm saying this need not be, and traction can be found even having more power than the 450. They want us to think this cannot be done. I refuse to accept that type of thinking and pray there are others out there who agree.
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Bah! Broader, more usable power, no real increase on top. This is more of the same pablum I've been seeing for the past few years, makes me want to puke. Spend a lot of your hard earned dough on a bike to make it "more" competitive with the 450 thumpers. It Narrows the gap a bit, so to speak. Well, so to speak, that is totally unacceptable! If I'm going to hop up a 250 to compete with a 450 thumper, it is not mission accomplished until I can pull that 450 through the gears, period! Think about it a moment. The Project 250 YZ would smoke this bike with the LA sleeve kit. It would simply run off and leave it, and it's still a genuine 250. No way would I spend hard earned money on anything that would not enable me to go head to head with a 450 and at the very least, be equal with it through the gears, and even that is too little.
Yeah theyre like "if you want to be compeditive you need to cheat and get a big bore"
And thats basicly what the thumpers are, way more cc to beat the two strokes
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Didn't Ohlins make a 360 cc kit for the YZ250 at one time?
Not sure if it was Ohlins, but yes... Hung out with Mickey Dymond back in 1989 at DeAnza when he was riding one. I think they even ran them in the 500 Nats at one point.
yes it was Ohlins.
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A long time ago I rode a buddie's Klemm 300 Honda CR250. My friend was sponsered most of the time, very fast, and knew what he was doing. The big bore CR was truly awful, like someone had shoved an old RM370 engine into the Honda frame.
I hate to sound like a broken record and some will argue (perhaps accurately) that the technology does not yet exist , but I am certain that a Direct Injected 125 or 250 two stroke would be competitive with the four strokes within the existing rules.To be honest, I think a D.I. 2s would anihilate a 4s of twice the displacement and so why don't they exist? I don't know, maybe the major manufacturers are unwilling to upset the 4s gravytrain in today's harsh economic climate.
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Yeah, its a good article, but you won't ever see them test it against a 4-stroke. Same thing with a big bore 125 or 150.
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I'm not willing to accept that twostrokes must be less powerful than 4strokes or they won't be able to get the traction needed to accelerate with them. The very thing I hear next is that we must have a bit less power to get traction, but the 4 stroke can get traction with more power. Hmm
This is not a conspiracy, but a simple fact. Four strokes (by virtue of making power with
every other stroke) are better at putting the power to the ground in most situations.
When you combine that strength with a big displacement advantage, the results are a
forgone conclusion.
As far as building 250 two strokes that can run with 450 four strokes; Remember when RC
was still running a two stroke and KDub was running a CRF? RC had one of the baddest
two strokes on the planet and was generally acknowledged as the fastest rider, yet he
had to work his ass off to beat KDub and occasionally lost to him. In the following years
after he switched to four strokes, He and Stewart just checked out from the rest of the
field and everybody else (including KDub), were racing for third. Same thing happened to
Travis Pastrana at the East/West 125 shootout. He and his Factory Suzuki lost to the
250F of a satellite team.
The AMA has given four strokes an unfair displacement advantage and the manufacturers
are pouring all of their R&D resources into four strokes, further widening the gap. If you
want to race heads up with a 450F, a Service Honda KX500 or CR500, can run with and
probably win against the 450Fs in the hands of a skilled, strong and well conditioned rider,
but we are talking about the open class not the 250 (or whatever it is called this week)
class.
While other sanctioning bodies regard parity and fairness above all else, AMA Pro racing
couldn't care less - never has.
dogger
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If the AMA would simply allow the 144s to compete with the 250Fs and big bore 250s (up to 344cc) to compete with the 450Fs then they could compete. Of course we know that will never happen, and you will never see MXA test these bikes against each other. But of course, everyone wants to see them tested anyway.
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Dogger, it sounds like you are then implying that it simply cannot be done. I disagree. I very much agree with Sachs. But whether DI, or some other method, we have to stop accepting limitations as if the current state of development of the 2stroke engine is as far as it can go. If they put even half the effort into seriously developing the 2stroke as the big 4 have the 4stroke, you'd almost certainly be seeing bikes that were far superior in every respect to current 2stroke machines. Very little serious effort is going into them.
Dogger, I didn't mean to imply that I thought it was merely a conspiracy that 4strokes get better traction. I've ridden both types of bikes over the years and I'm well aware that this is generally true. This can be a liability to them at times, in deep sand, as I found out years ago on the old TT 500 Yamaha. That bike would often dig a hole and sit in it on sand hills that old 250 2strokes of the day, were simply skimming right up. Nevertheless, What I'm saying, is that we need to explore other avenues for getting power to the ground than simply rolling over and accepting having less power and hoping to overcome this by better handling. Flywheels, different tires, whatever. Simply because it hasn't been done doesn't mean it cannot be done. If so, then Project 250 and any other efforts of that type are simply wasting money and time, and we should just give in and buy a thumper.
If the AMA is not going to change the rules, we've got to come up with better 2stroke technology than we've currently been using. Make no mistake, the 4strokes will get faster and better. If we can't get folks to focus back on the 2stroke pretty soon, they may very well get the 4stroke to the point where it is equal to or better in power to even the same sized 2stroke -- as 2strokes currently sit. Even now, we can see this with the new KTM 350. Next thing you know, we may be seeing a revolutionary new thumper that is a 250, putting out every bit as much peak power as the current KTM 250 SX 2stroke. We've got to get the general public to where they are demanding 2strokes again, so that the big factories, or somebody with the wherewithal, will start putting some serious research and development into the engines. I honestly believe if this doesn't happen pretty soon, it never will, and the 2stroke truly will go extinct. I don't believe that making a 250 2stroke which can both out-accelerate a 450 4stroke, and get power to a dirt surface well enough to do so, is the equivalent of trying to make a square circle. It seems, however, that a number of posters on this site believe just that though, that it cannot be done. I'm positive it can.
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While i agree turuine that 4 strokes will get better i dont think they will be able to get them to the same horsepower level as the current 2 stroke in a mx bike.
For road racing yes. But MX is a totally diferent animal.
Peak horsepower is not the only goal.
Yes 250 4 strokes can make good horsepower these days but they need big rpm's to do it.
For them to make more power they need more rpm's and the motors are on the edge of current metallurgy capalbilities now.Thats why they blow up so spectaculary now. Any further exotic materials will just make them even more expensive.
If 250F's pulled even more rpm's then now they would have a shorter power band then what current 2 strokes have.
And thats the biggest complaint of smokers.
Again fine for road racing but counter productive on a MX track.
If you look at the torque outputs of current motors the 250F has about 19ft/lbs a 250 smoker has 28ft/lbs and a 450 has 31ft/lbs.
The 250 smoker needs to be able to put down on the ground easier.
I think a DI motor with maybe the Honda exp idea as well would work wonders.
The motor could by tuned to match a 450 but the DI system would make the motor less peaky and so more manageable.
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If my memory is correct the BMEP of a 4s is higher then of a similar 2s which means a 4s is a slightly more efficient powerplant then a 2s. However,due to the 2s cycle, a 2s performs effectively twice as much work per unit time as a 4s. To offset this, the manufactures are spinning the 4s almost twice as fast as the 2s (never mind discpl. advantages). Herein lies the Achillie's Heel of a 4s,the motors are (as TMKIWI pointed out) virtually up against a brick wall in terms of current cost related technologies allowing any further increases in engine speed.
A highly tuned DI 2s would have significantly reduced lower rpm scavenging losses then a current 2s.A DI 2s would feel "very torquey" at lower rpms and then (due to injection timing lags still requiring an expansion chamber) would come on in a "rush" at higher rpms with slightly more peak power then a current 2s. Fuel economy would be significantly better and the motor would still have 2s "hit".
What this means, and I'm speculating here, is that a DI 250 2s would probaly match a 450 4s in terms of breadth of torque curve,generate similar peak hp figures and the peak torque values would exceed that of a 450 4s. All this with less weight and no fear of dropping a valve when you're hitting that next double (jump).
And so, and bear with me as I repeat myself, with DI technology I am certain we could beat the 4s's at their game within the framework of their rules. Somewhere on this planet somebody has the resources to make a next generation 2s MX'r a reality.
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I have heard that L.A sleeve is proto typing a 330cc bolt on kit for the YZ250`s . :o
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Dogger, it sounds like you are then implying that it simply cannot be done.
I don't mean to imply that. I guess I'm not convinced that a fight against unfair rules
and a stacked deck (manufacturers) is a good idea. I also don't think more power will
cure what ale's you. I could probably write several boring pages on the pros and cons
concerning the horsepower debate but there is so much more to going fast. That's
why the O' Show was able to beat all those works 250s and 500s heads up on a 125
at the des Nations years ago
I have raced all of the bikes we have discussed. I switched to four strokes because it
was costing me a fortune to modify my 250 two strokes enough just to stay with a fast
guy on a STOCK 450F. The four years I competed on the four strokes saw my race budget
double, my injury rate go up and my fun factor go down. I wised up and switched back
to two strokes for good.
The purpose of the last paragraph is to show you and others, there are hundreds if not
thousands of people like me that have done the same and I believe it is a growing trend.
Regardless of the spooge you read in the "message controlled" media, two strokes are
alive and well. One of the very popular series in SoCal right now is Marty Tripes 100cc
racing (all two strokes).
Instead of banging our heads against the wall trying to overcome arbitrary BS displacement
rules, I think we should consider the establishment of another sanctioning body that would
allows heads up racing. That would put the fun back in racing by allowing all bikes to
compete in a 125, 250 and open class regardless of their exhaust note. MX is a grass
roots kind of sport to begin with, we should go back to those "roots". Since when should
the AMA and a collection of Japanese manufacturers dictate what kind of bikes we
ride/race?
Let the big four rake in the profits from the ever escalating cost of the four strokes. We
don't have to participate. Eventually, they will price themselves out of reach for most
people. This is a recurring theme in all forms of racing, one that is usually met with rule
changes to get cost under control: F1, CART, even the AMA (remember works bikes?).
Sometimes the changes work, F1 is as popular as ever. Sometimes the changes are a
disaster, does anybody care about the Indy 500 anymore?
This is just my two cents, another point of view and the way I would like to see this mess
play out.
dogger
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i think 250 two strokes should be in the 250 class! and 500 2 strokes in the open class and 125s in a 125 class, not 250s in the open, and 125s in the 250s, the classes should be judged on the CCs the bike has not the power
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If there's anything to be leaned from those 4 strokes is that having a explosive hard hitting powerband is not realy necessary to turn out fast lap times.
Corner speed and traction is were it's at, not dragracing from turn to turn
If thats the case why do they need 2 x bigger engines to win over 2 strokes? wouldn't the traction & corner speed make them competative at a cc v cc level... obviously not
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A 250 2 Stroke is, and always has been, fast enough to win if the rider has the skill to identify and use the characteristics of the bike to their greatest advantage.
Yes, there were times in 03 where RC had to work to pretty hard to stay in front of Kevin. But there were also plenty of times in supercross 04 including places like Daytona, where Reed toyed with him and his tractor bike and then slam-dunked them easily, and later on in 05 when poor K-Dub was almost lapped traffic for RC, Reed and Stewart on their 2 stroke mounts. And... The 4 strokes were just as powerful back then (05) as they are now. They couldn't compete against the 2 strokes that were on the line against them though.
I feel that the conversion of all the major players for SX 06 was probably driven by the actions and agendas of the manufacturers. Like maybe the Yamaha riders had a "Choice" up through 05, and then after that it became more of a "Yamaha pulled their support for Fred Andrews Racing because they wouldn't run a WR250F..." type situation. Whatever it is, it stinks, and it has made supercross considerably less exciting no matter what you hear TV announcers and race promoters say.
KTM 250sx helmet cam - tmc mx 8/16/09 250A 2nd moto (http://www.youtube.com/watch?v=caXju8S6uO0#)
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http://www.racerxonline.com/article/944.aspx (http://www.racerxonline.com/article/944.aspx)
So, I was bored and am working my way through all the 'Ask Ping' columns on RacerX.
Found this from October 06...
Ping,
I know Iā??m beating a dead horse here, but why canā??t the motorcycle industry see the value in the two-stroke? We as consumers are killing those low-center-of-gravity, high-revving oil-burners (man, I still love that smell) by falling for the marketing genius of the factories. They must be loving it! They seem to give all the advantage to the thumpers. ā??First, letā??s double the ccā??s so they can get some serious power out of those things, then lets take away the leaded gas that is the lifeblood of the oil burner to make power.ā? Man, talk about a slap in the face! They even rename the stinkinā?? classes we race in for Godā??s sake! All of this is going to add up to a sport that no longer has an entry-level bike. We now have 80cc bikes that must compete with a 150cc bike, and the price is, again higher yet than the 80. They have pretty much already killed the 125 (yet again, less money than the 250F). You for sure should have some love for the 125ā??#90 in, oh say, ā??94 Unadilla?
For a challenge, I would like to see all race organizations have two-stroke-only classes of their own. This means you, Coombs. Oh, and what about the ā??Four Stroke Nationals?ā? Like thatā??s a big deal anymoreā??I can see that any weekend at my local track. Why not the Two-Stroke Nationals with some serious contingency pay. Better yet, why donā??t we even things up a bit and allow, oh, say, a 295cc (or so) bike to compete with a 450F and a 167cc bike to compete with a 250F in the Nationals? (Man, Iā??m getting fired up!) That should keep it close down the start for a bike that is just over half the displacement of the other. I hate to say it, but maybe the GNCC guys are the smart ones, as they seem to be the only loyal onesā??Iā??m not a sheep in the flock.
R.M. (Yes, a two-stroke). Boise, Idaho
Dear RM,
I like your energy, Mr. Two-Stroke, I really do. Iā??ve been slow to accept the industry revolution to four-stroke bikes since their inception. I still ride two-strokes as much as possible and on many occasions because I have more fun on them than on a thumper. I think a lot of people are realizing that they enjoyed their old bikes and are switching backā??Iā??ve heard quite a few people tell me that, anyway. Unfortunately, itā??s too late. The manufacturers made a decision to go down the valve-and-cam road and there isnā??t any going back. Fuel injection will be a standard item in the next two to three years and, as technology continues to advance, so do the price of the bikes. It wonā??t be long before we are paying $10,000 for a dirt bike. That is a scary thought.
And I hate to rain on your parade, but I think some of the GNCC race teams, including two-stroke holdout Yamaha, will be competing on four-stroke bikes next year. The whole situation almost makes me want to quit riding bikes. Almost.
PING