...another 4t vs 2t debate but diff take on it

drt410
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drt410
So say they allowed you to run 250s in the 250 class...etc and even it up. 2 strokes are so simple what can you really do that they havent? The 4 strokes jusssst started adding finger followers allowing for much more aggressive cams than weve seen so far. You can have single cams like the ktm with basically forked roller rocker arms from a central cam- which Idk how this makes so much power as the simplest head, but it works and its light. Then the Crf450r has the single cam over the intake with a rocker arm going to the exhaust valves. Then you go all the way to the 19’ Kx450 which uses superbike tech with roller rockers now on both cams like the crf250r also uses now which is as high tech a dohc cam setup as it gets and the most high tech in each respective class from those 2 engines.

For 2 strokes you can do direct injection, which they say makes it ride more like a 4 stroke which imo if they want to be competitive thats not a bad thing. Then what an electronic power valve? Maybe have a couple... Maybe better reed valve systems which i dont think direct injected would even need Im not sure. Then obviously elec start. Ive heard theres things they can do with pistons, but what more can you really unlock in an engine with no cams? Anyone know any new 2 stroke tech that would be going into these bikes if they were still used?
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jeffro503
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jeffro503 8/15/2018 7:42pm
8/15/2018 7:42pm
drt410 wrote:
So say they allowed you to run 250s in the 250 class...etc and even it up. 2 strokes are so simple what can you really do...
So say they allowed you to run 250s in the 250 class...etc and even it up. 2 strokes are so simple what can you really do that they havent? The 4 strokes jusssst started adding finger followers allowing for much more aggressive cams than weve seen so far. You can have single cams like the ktm with basically forked roller rocker arms from a central cam- which Idk how this makes so much power as the simplest head, but it works and its light. Then the Crf450r has the single cam over the intake with a rocker arm going to the exhaust valves. Then you go all the way to the 19’ Kx450 which uses superbike tech with roller rockers now on both cams like the crf250r also uses now which is as high tech a dohc cam setup as it gets and the most high tech in each respective class from those 2 engines.

For 2 strokes you can do direct injection, which they say makes it ride more like a 4 stroke which imo if they want to be competitive thats not a bad thing. Then what an electronic power valve? Maybe have a couple... Maybe better reed valve systems which i dont think direct injected would even need Im not sure. Then obviously elec start. Ive heard theres things they can do with pistons, but what more can you really unlock in an engine with no cams? Anyone know any new 2 stroke tech that would be going into these bikes if they were still used?
I can't really answer some of that because it's above my pay grade. But as far as 2 stroke technology goes in MX , you really need not look further than what KTM / Husky are doing. Along with the YZ's and TM's. All of them are extremely capable in the right hands , but you have to know how to ride them. They are a different beast to ride , as a 250F is pretty easy to ride. But again , in the right hands , a newer 250 2 stroke is capable of running right with 450's , minus maybe the top 10 in a national. Look at what Chris Alldredge did before he got hurt.
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ledger
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ledger 8/15/2018 9:25pm
8/15/2018 9:25pm
Add engine braking, nah, just kidding.
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Solidkm
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Solidkm 8/15/2018 9:31pm
8/15/2018 9:31pm
Bruce372 wrote:
I hope more electric bikes come out.
Just threw up in my mouth. I am sure there is a quad forum somewhere you could go play on
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Bruce372
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Bruce372 8/15/2018 9:44pm
8/15/2018 9:44pm
Bruce372 wrote:
I hope more electric bikes come out.
Solidkm wrote:
Just threw up in my mouth. I am sure there is a quad forum somewhere you could go play on
Lol. I've got 4 gas bikes in my garage mate. The constant moaning of 2 and 4 debate is incredibly dull.
drt410
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drt410 8/16/2018 1:24am
8/16/2018 1:24am
drt410 wrote:
So say they allowed you to run 250s in the 250 class...etc and even it up. 2 strokes are so simple what can you really do...
So say they allowed you to run 250s in the 250 class...etc and even it up. 2 strokes are so simple what can you really do that they havent? The 4 strokes jusssst started adding finger followers allowing for much more aggressive cams than weve seen so far. You can have single cams like the ktm with basically forked roller rocker arms from a central cam- which Idk how this makes so much power as the simplest head, but it works and its light. Then the Crf450r has the single cam over the intake with a rocker arm going to the exhaust valves. Then you go all the way to the 19’ Kx450 which uses superbike tech with roller rockers now on both cams like the crf250r also uses now which is as high tech a dohc cam setup as it gets and the most high tech in each respective class from those 2 engines.

For 2 strokes you can do direct injection, which they say makes it ride more like a 4 stroke which imo if they want to be competitive thats not a bad thing. Then what an electronic power valve? Maybe have a couple... Maybe better reed valve systems which i dont think direct injected would even need Im not sure. Then obviously elec start. Ive heard theres things they can do with pistons, but what more can you really unlock in an engine with no cams? Anyone know any new 2 stroke tech that would be going into these bikes if they were still used?
jeffro503 wrote:
I can't really answer some of that because it's above my pay grade. But as far as 2 stroke technology goes in MX , you really...
I can't really answer some of that because it's above my pay grade. But as far as 2 stroke technology goes in MX , you really need not look further than what KTM / Husky are doing. Along with the YZ's and TM's. All of them are extremely capable in the right hands , but you have to know how to ride them. They are a different beast to ride , as a 250F is pretty easy to ride. But again , in the right hands , a newer 250 2 stroke is capable of running right with 450's , minus maybe the top 10 in a national. Look at what Chris Alldredge did before he got hurt.
The new ktm/ yamaha 2 strokes make 1 more horsepower since like 2001.
kawasa84
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kawasa84 8/16/2018 1:51am
8/16/2018 1:51am
Well the snowmobile industry is still improving on 2 stroke technology. The direct injection is one they've been using now for at least a couple years.
Of course Boyeson and Moto Tassanari make after market, (sometimes OEM) reeds for them.
The industry is also moving ahead with how they channel lubrication to the bottom end, with atomized and computer regulated misting of the rotating crank and rod, since they lack a transmission like an MX bike.
The typical horsepower from the 800 cc twins put out 155-160 and now the 850 cc's are putting out up to 180 hp.
So, with that, maybe some of that could cross over.
JustMX
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JustMX 8/16/2018 3:31am
8/16/2018 3:31am
The biggest technological hurdle of the two strokes is having them make a farting noise like the 4 strokes.
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clem
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clem 8/16/2018 7:44pm
8/16/2018 7:44pm
I would have to think that they could get more out of the single cylinder 2 strokes but they may not be rideable on the dirt. Factory 250cc gp road bikes were making near 100hp in their last years on the circuit. Being that most mid 2000's motocross 4 stroke tech was developed on the road race side, I would think that the 2t's could benefit from the later 2 stroke monsters of the gp's.
kunk
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kunk 8/16/2018 7:53pm
8/16/2018 7:53pm
clem wrote:
I would have to think that they could get more out of the single cylinder 2 strokes but they may not be rideable on the dirt...
I would have to think that they could get more out of the single cylinder 2 strokes but they may not be rideable on the dirt. Factory 250cc gp road bikes were making near 100hp in their last years on the circuit. Being that most mid 2000's motocross 4 stroke tech was developed on the road race side, I would think that the 2t's could benefit from the later 2 stroke monsters of the gp's.
The GP bikes were not singles
clem
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clem 8/17/2018 5:31am
8/17/2018 5:31am
clem wrote:
I would have to think that they could get more out of the single cylinder 2 strokes but they may not be rideable on the dirt...
I would have to think that they could get more out of the single cylinder 2 strokes but they may not be rideable on the dirt. Factory 250cc gp road bikes were making near 100hp in their last years on the circuit. Being that most mid 2000's motocross 4 stroke tech was developed on the road race side, I would think that the 2t's could benefit from the later 2 stroke monsters of the gp's.
kunk wrote:
The GP bikes were not singles
I realize that. The nsr250 engine always looked like a twin cylinder CR125. I was just trying to point out that there may have been some tech in those bikes at that time that did not trickle down to motocross.
TJMX947
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TJMX947 8/17/2018 7:08am
8/17/2018 7:08am
We had a really good convo a few months back where I asked a similar question in regards to the hierarchy of two stroke modifications and tuning. Derek Harris basically took us all to school on the subject. He referenced development in two stroke GP bikes and the loop holes teams/factories have used to stall development. My biggest take away from his "vital gold" was that pipe design is a huge indicator of how far you can go in the realm of horse power, and what I've noticed as I've looked at two stroke jetskis is the tuners use bigger pipes because they have room for them (motocross bikes are somewhat limited in this area).

He confirmed the design of the KTM125 being light years ahead and that with a specific amount of money it wouldn't be out of the question to get either 45 or 50 HP. It wouldn't be cheap but he said its doable.
mx_563
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mx_563 8/17/2018 7:24am
8/17/2018 7:24am
The so called 4-stroke "technological development" of the last 20 years, as it pertains to dirt bikes, seems a bit of a misnomer. To me it seems that what we've been seeing is simply implementation of existing technologies and knowledge.

If I'm not mistaken, there are theoretical max efficiency values that can be calculated based on the potential energy in the fuel, and the heat of combustion, friction losses, and some other fancy math/physics. I'm pretty sure we are already very close to the maxing out what an ICE can deliver. Just like with weight savings you reach a point where it gets to be very expensive to make even the slightest gain. When economics don't matter (F1) you can keep pushing that envelope. But in our (dirt bike) world, I think we're pretty damn close to reaching practical limits.

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