Two-strokes back in 2011 US Supercross

[lankydoug]

A similar argument can be made that a four stroke is not making compression when the valves are open. Or how about that it's not practical for a 2t to make the same static compression as a 4t (like 12:1 or greater in most cases) because of the need for the piston port. I say let's measure total displacement and go racing with no unequal rules, the rest will sort itself out.

 

[LawnDartMike]

I agree - a 250 and 450 class for all engine types. Let them be judged at the finish line.

 

[Troy F Collins]

Another Factor is the 4T crankshaft has to go around twice for every power stroke ...which gives the rear tire enough time to regain traction between power strokes....

if the rules were heads up(same displacement)at the beginning of the 4T revolution..ie 125 or 250 the 4T revolution would have never happened

but the environmental changes needed with particular regards to a total loss 2T oil system and the user friendly powerbands of the 4T...made the change very easy to swallow.....so they are here to stay

but the 4T isnt perfect.....its louder and the sound carries....and thats another set of issues altogether

change on the horizon..??? I dont think so

Glad the Europeans kept the 2T alive..though

 

[ohmygewd]

If the 2ts were competitive, you'd see the top level independent teams, like CR's and Joe Gibbs etc. running them, as they aren't subject to toeing the factory line.
Would the top riders prefer riding a current 2t bike that weighs 30lbs less than a 450 4t? Certainly. But they won't win on it, unless everyone else follows suit. It's not 2005 anymore, 4t's have improved immensely since then and Windham hasn't exactly been the (consistently) fastest guy out there, ever, so it doesn't work to compare him on a 4t 5 years ago to guys that are/were naturally much faster riders. JS, RC, CR etc. aren't/weren't racing against KW, They were/are racing against each other. If Bubba shows up on a 250 2t against CR, RD, RV etc. on 4ts, he'll lose to them even though he'll still be faster than half the field (the slow half).

I think you have answered your own question about why independents don't run 2t's IS because technology has moved and the fact that that any particular manufacturer doesn't spend the necessary R&D dollars in 2t's makes them redundant.

That being said, if someone comes out with a 250-300 DI 2t with extensive computer controls, which improve it's power delivery and outright power output to the 60+hp level that the factory 450s get then you might have something.......
At big outdoor tracks- especially fast flowing natural terrain ones, a 2t has a better chance at being competitive as they can maintain more momentum & outright drive out of corners generally isn't quite as paramount. That's part of the reason why they're still popular in cross country, HS & GNCC events.

Absolutely correct, unless manufacturers start to reinvest in R&D into 2t's with DI etc, and also steering/frame geometry, then a 2t won't be competitive at the top level MX/SX. Even if you take the displacement down to 350 4t vs 250/300 2t, it's all about the power to the ground and useable tractability vs explosiveness.

Look in the last tens years of 4t's v 2t's:
4t's
Gone from 400 to 450.
Gone from carb to EFI.
Gone from CDI to programmable ignition.
Constant frame/geometry changes.
Constant development in engine parts material.
Constant development in suspension.
Some have changed the engine position/mounting.
Some have changed the direction of the crank spinning.
Etc
Etc

2t's
No change in engine design.
Japanese manufacturers have not invested in 2t's for nearly a decade now...don't tell me the 'new' yz250 is any different to the one that was sold in 05?
Performance part manufacturers haven't invested in 2t's as the market shift is 4t's.
KTM have been the only company to make an investment into 2t development over the decade whlist others have just dressed them up....still the KTM250SX is a PDS unit?

In short, whilst l love my 2t's, factory and top independent MX/SX teams will never run a 2t unless they themselves know the manufacturer is investing in that technology and that flows onto the performance market.

What is driving the masses back to 2t's is quite simple, maintenance or perceived ease and cost of maintenance....if the masses continue to buy euro 2t's then the big 4 will respond by reinvest into 2t's again

 

[water racer]

Oh great.... We now have a never ending 2t-4t argument just like the orange site.
GP

 

[hammer]

Not sure if this has been posted before. It's a good read.
http://www.dirt-bike-tips-and-pics....ml?utm_source=vitalmx.com&utm_medium=referral

 

[ray_ray]

I'll go with what I heard Mitch Payton say ... Which ever type engine the big boys go with and spend the most money on will win ... He does not care which it is only that the playing field should be level ... Having both engines performing at the top level will be very hard for a team like his because he can't really afford to develop technology for 2 different types ...

So a 250 2T can't beat a 250 4t? Ignorance is a curable thing in this case , bring on the racing ... I can even tell my bad a$$ 08 TXC250 4T runs like a 125 2T sometimes ... My 02 CR250 2T never ran like a 125 ...

I'm glad a 4t exists today because it is so easy to ride on the street and trails ... they will just purr along like a little kitty cat .. a 250 2T is just a beast to ride ... It just don't want to go slow ...

 

[Vinduro]

I agree - a 250 and 450 class for all engine types. Let them be judged at the finish line.

I feel 4 strokes need a slight displacement advantage but not a 100% or double displacement. I feel that a 40% rule would be fair. That would put 175cc 4 strokes against 125cc 2T bikes and 350cc 4T against 250cc 2T bikes. I feel that would be fair but not what is in place now. What is in place now was done to give a 4t a significant advantage over the 2T. Not make it even.

In AHRMA Vintage racing they allow 150cc 4T against 125 2T and 120cc 4T against 100cc 2T bikes. I think they allow 300cc 4T against 250 2T bikes.

 

[bearorso]

I feel 4 strokes need a slight displacement advantage but not a 100% or double displacement. I feel that a 40% rule would be fair. That would put 175cc 4 strokes against 125cc 2T bikes and 350cc 4T against 250cc 2T bikes. I feel that would be fair but not what is in place now. What is in place now was done to give a 4t a significant advantage over the 2T. Not make it even.

In AHRMA Vintage racing they allow 150cc 4T against 125 2T and 120cc 4T against 100cc 2T bikes. I think they allow 300cc 4T against 250 2T bikes.

Vinduro,

I know who you are, and have a lot of respect for you and your achievements.

But, I believe there should be no capacity advantage given , whatsoever, to 4ts.

They are no longer foo foo bikes. AHRMA needs things like that because the 4ts, for the most part, were / are foo foo bike based engines. Though the 2ts are also primitive. Don't get me wrong, I grew up with BSAs,CCMs and all sorts of bikes around me, and was one of those 'crazies' that raced with Hybrid XR / CR bikes. The modern 4t engine needs No capacity advantage given to it.

They have natural advantages over an equal displacement 2t, just as an equal displacement 2t has advantages over the 4t. I think it pretty well evens out, with current levels of development of either type of engine.

Both types have a lot more to come in development (the 2t more, purely because it has been stagnant for so long).

From an engineering perspective, racing is about improving technology. Let the battle Recommence with equal capacities (Rotaries - which I know you've ridden - and other ICE engines as well, but it will, logically, come down to 2t / 4t) and let either engine type try to win, with no artificial constraints / handicapping. of either.

 

[lankydoug]

Vinduro,

I know who you are, and have a lot of respect for you and your achievements.

But, I believe there should be no capacity advantage given , whatsoever, to 4ts.

They are no longer foo foo bikes. AHRMA needs things like that because the 4ts, for the most part, were / are foo foo bike based engines. Though the 2ts are also primitive. Don't get me wrong, I grew up with BSAs,CCMs and all sorts of bikes around me, and was one of those 'crazies' that raced with Hybrid XR / CR bikes. The modern 4t engine needs No capacity advantage given to it.

They have natural advantages over an equal displacement 2t, just as an equal displacement 2t has advantages over the 4t. I think it pretty well evens out, with current levels of development of either type of engine.

Both types have a lot more to come in development (the 2t more, purely because it has been stagnant for so long).

From an engineering perspective, racing is about improving technology. Let the battle Recommence with equal capacities (Rotaries - which I know you've ridden - and other ICE engines as well, but it will, logically, come down to 2t / 4t) and let either engine type try to win, with no artificial constraints / handicapping. of either.

Amen brother!

 

[ray_ray]

Cedric Soubeyras got hurt ... something with a crash and some bone chipping , so his riding here as been postponed till later in the season ..

UPDATE: No racing till next yr due to this injury ?...