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Offline 2stroker

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motocross action mag
« on: June 17, 2010, 03:52:51 AM »
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

Offline Coop

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Re: motocross action mag
« Reply #1 on: June 17, 2010, 04:52:31 AM »
Cool article and good looking bike.
- Mike - Don't take life so seriously, nobody gets out alive.

Offline SachsGS

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Re: motocross action mag
« Reply #2 on: June 17, 2010, 05:10:55 PM »
Didn't Ohlins make a 360 cc kit for the YZ250 at one time?

Offline riffraff

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Re: motocross action mag
« Reply #3 on: June 17, 2010, 05:34:18 PM »
Not bad for modern media, wonder when the 330 kit will available?
aaahhhhh yes, I remember the good old days

Offline 6IX

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Re: motocross action mag
« Reply #4 on: June 17, 2010, 08:12:55 PM »
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.

Offline TMKIWI

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Re: motocross action mag
« Reply #5 on: June 17, 2010, 08:36:05 PM »
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
If you don't fall off you are not going hard enough

Offline Turquine

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Re: motocross action mag
« Reply #6 on: June 17, 2010, 10:45:46 PM »
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.

Offline scottydog

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Re: motocross action mag
« Reply #7 on: June 17, 2010, 11:52:19 PM »
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

Offline Turquine

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Re: motocross action mag
« Reply #8 on: June 18, 2010, 12:48:06 AM »
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
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.

Offline losec

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Re: motocross action mag
« Reply #9 on: June 18, 2010, 03:49:24 AM »
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
I never crash -I just make unexpected decelerations

Offline admiral

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Re: motocross action mag
« Reply #10 on: June 18, 2010, 06:14:49 AM »
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.

Offline SachsGS

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Re: motocross action mag
« Reply #11 on: June 18, 2010, 06:50:24 AM »
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.


Offline burn1986

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Re: motocross action mag
« Reply #12 on: June 18, 2010, 08:57:19 AM »
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.

Offline dogger315

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Re: motocross action mag
« Reply #13 on: June 18, 2010, 09:24:34 AM »
Quote
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

 
« Last Edit: June 18, 2010, 02:06:54 PM by dogger315 »

Offline burn1986

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Re: motocross action mag
« Reply #14 on: June 18, 2010, 01:59:48 PM »
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.