Correct AMA 2 Stroke displacement

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3/19/2018 9:27 AM

I have been thinking lately, the AMA admits that when introducing 4 strokes that they killed the 2 stroke by allowing too large of displacement on 4 strokes.

Looking back what do you think would have been the correct size of 4 strokes in both classes so that both 4 strokes and 2 strokes could have remained competitive?

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3/19/2018 9:34 AM

175/200 and 300/350 IMO

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3/19/2018 9:44 AM
Edited Date/Time: 3/19/2018 9:46 AM

125T/200F

Just by basic math, a 250F to 200F is a 20 percent reduction in engine size...a 20 percent reduction in power would put a stock 200F around 32HP and a full race bike close to 40HP...

300T/350F

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3/19/2018 9:47 AM

125/125
250/250

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3/19/2018 9:52 AM

ktm125 wrote:

125/125
250/250

+1

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3/19/2018 9:56 AM

They could fix it now with no “allowance”

Up to 250cc
Up to 500cc

The extra power of the 2 stroke, is offset by the wide power band and easy delivery of the 4 stroke.

In Australia they were allowing 250 2T’sto race against 250 4T’s. Although marginally faster (in most drag races) and cheaper, the 2Ts didn’t dominate. As far as I’m aware.

I heard a commentator claim the top 250f’s are 52hp!
A lot cheaper to get 52hp out of a 250 stroker. Maintenance would be a fraction of the cost.

In the “up to 500” class. Choose 450 4t (big bore if you feel capable), or 250/300/ what you think you need 2T

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3/19/2018 10:04 AM

ktm125 wrote:

125/125
250/250

This.
CC for CC.

While the 4 stroke won't make the peak power a 2 stroke will, the powerband will be broader and easier to ride. The higher the power levels, the less the peak power numbers mean. A 50hp 4 stroke 450 will be easier to ride and arguably turn faster lap times than a 65 hp 2 stroke 500 (or 450 pinger), while in the smaller displacement classes the overall power becomes more important.

This means the 125 class would be all 2 strokes, while a 450 class would be almost all thumpers. The 250 class would be a smattering of both engine types, imo. I think it would make for really exciting racing.

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3/19/2018 10:10 AM

Oems got some people in their pocket or it would have been rectified 10 yrs ago..

and now with no japanese engineers driving inovation,
and thus competition.
we have no idea where a 2018 2 t would be in comparison to a 4t...

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3/19/2018 10:23 AM

ML512 wrote:

125T/200F

Just by basic math, a 250F to 200F is a 20 percent reduction in engine size...a 20 percent reduction in power would put a stock 200F around 32HP and a full race bike close to 40HP...

300T/350F

Is the power curve linear like that?

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3/19/2018 10:27 AM

Huh...I must have missed the part where the AMA "admitted" that. Maybe you can point me in the right direction.

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3/19/2018 10:32 AM

Make 250 the premier class. 250 two-strokes are welcome. Any VP fuel available to the public is ok!

Make the support class a 150 class. 150 two-strokes and four-strokes are welcome. Any VP fuel available to the public is ok! Sleeve down 250Fs or design a new engine and plug into the existing chassis. Big-bore a 125, port and polish, and you are good to go.

Also have a support 450 class for privateers only.

If four-strokes are better machines, they won't have a problem running at equal displacement.

Factory riders are ineligible for Feld/AMA purse money. Funnel that money to non-factory supported riders (based on finishing positions) to help level the playing field. Rank and file riders need that money to get from race to race, proper training/nutrition/rest, insurance, equipment, and such. Elite factory riders do just fine with salaries, bonuses,endorsements, and the like.









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"Thank God my father wasn't rich."
-Hurricane

"You wouldn't take clay to Southwick, so why take sand to Red Bud?"
-DV

"I ride a two-stroke because I am Weigandt-level cheap"
-Me

3/19/2018 10:36 AM

Should be equal because 4 strokes are the greatest things ever. Remember?

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"A link is only as long as your longest strong chain"

3/19/2018 11:05 AM

I remember the theory that a four stoke should get double the displacement since it fires only once every other revolution, but let's not forget to factor in that when a two stroke fires, it makes power from maybe 50% of the power stroke as it exposes the exhaust and intake ports half way down, therefore, it's true power is not from the full displacement of it's capacity. Sound fair?

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3/19/2018 11:14 AM

They let them have double when the only real options were an XR or an ATK. There is an MXA interview with Decoster in the late 90s where he says that the correct displacement for the then 250 2 stroke class should have been around 350 for the 4 stroke. This is when the debate was just looking at the YZF 400/426.. a years before the 250f thing happened.

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3/19/2018 11:23 AM

Yamaha was already winning races with a 400cc machine yet the AMA STILL allowed Honda to bring in a bigger 450 machine even though the YZ400 was already proven competitive by Doug Henry. They should have capped it at 400cc and went with 125/200 and 250/400 classes imo. Now we have the 250's as the stepping class which is just all wrong....

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3/19/2018 11:27 AM

I would think accepting the 2 stroke era in supercross is over is the best idea.

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3/19/2018 11:38 AM

Remember KTM's 520SX?! I remember going to RedBud back in 00 or 01 and I believe Paul Carpenter and possibly John Down were riding one of those and were clearing Laroccos Leap at what sounded like quarter throttle haha. I had 2 KTM 520 SX's and that motor is hands down my favorite motor I've ever ridden on.

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3/19/2018 11:49 AM

By allowing the increased displacement when considering the thumps we all know what happened. The new 4 strokes with double displacements have increased dramatically in power and traction. So the 2 strokes are well out performed by their classmates with larger displacements. There had been talk about allowing the 2 strokes to run more cc's in order to catch up. IMO that is a mistake.

They need to make the two classes what they have been all along. 125 and 250. And let the manufacture's figure it out from there. Don't manipulate the race series to accommodate the manufactures. Give them plenty of time to prepare to lessen the impact it will have on them. The racing will be better. The speeds will be slower. The sport will be a tad safer.

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3/19/2018 12:09 PM

2 stroke guys will never be happy, no matter what.

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3/19/2018 12:12 PM

GuyB wrote:

Huh...I must have missed the part where the AMA "admitted" that. Maybe you can point me in the right direction.

They sort of did, by permitting EQUAL displacement racing at the Amateur level !!!! The attached is from the AMA's own magazine.

I believe it's just MX Sports that keeps the ridiculously outdated "Double-Displacement Rule" in Professional Racing.

Photo

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3/19/2018 12:17 PM

Bry145 wrote:

Make 250 the premier class. 250 two-strokes are welcome. Any VP fuel available to the public is ok!

Make the support class a 150 class. 150 two-strokes and four-strokes are welcome. Any VP fuel available to the public is ok! Sleeve down 250Fs or design a new engine and plug into the existing chassis. Big-bore a 125, port and polish, and you are good to go.

Also have a support 450 class for privateers only.

If four-strokes are better machines, they won't have a problem running at equal displacement.

Factory riders are ineligible for Feld/AMA purse money. Funnel that money to non-factory supported riders (based on finishing positions) to help level the playing field. Rank and file riders need that money to get from race to race, proper training/nutrition/rest, insurance, equipment, and such. Elite factory riders do just fine with salaries, bonuses,endorsements, and the like.









Nitro and Methanol too? It is available to the public after all....

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Tomac and/or Anderson for 2020.....

3/19/2018 12:48 PM

BobPA wrote:

Nitro and Methanol too? It is available to the public after all....

Wouldn't that require a gigantic fuel tank and/or pit stops?

I would think that C12 & MR12 would be preferable and affordable.

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"Thank God my father wasn't rich."
-Hurricane

"You wouldn't take clay to Southwick, so why take sand to Red Bud?"
-DV

"I ride a two-stroke because I am Weigandt-level cheap"
-Me

3/19/2018 1:01 PM

GangGreen wrote:

They sort of did, by permitting EQUAL displacement racing at the Amateur level !!!! The attached is from the AMA's own magazine.

I believe it's just MX Sports that keeps the ridiculously outdated "Double-Displacement Rule" in Professional Racing.

Photo

In a 1998 MXA article, Roger Decoster said the max displacement should be 360 for four-strokes. Had it been capped there, and leaded fuel was still allowed, the four-strokes likely would have never taken over.

The 125 class should have capped four-strokes at around the same scale, at around 175ccs.

I just can't understand taking a sport that is expensive to begin with and making it more expensive. This benefits rich folks who can afford to race any machine they like, but people with less resources will be priced out of the sport. And at that point OEMs, promoters, and the aftermarket have less customers and have to increase prices to make up for it. It is a vicious cycle.

Just imagine if pee-wee racing went all four-stroke. How could parents afford it?

Where does it all end? Electric bikes? That would be better than four-strokes. Of course two-stroke racing was the best of all, all things considered.




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"Thank God my father wasn't rich."
-Hurricane

"You wouldn't take clay to Southwick, so why take sand to Red Bud?"
-DV

"I ride a two-stroke because I am Weigandt-level cheap"
-Me

3/19/2018 1:46 PM

Im more concerned with Electric bikes and how they'll regulate that direction.
200cc 2 stroke for the lites class is what I think would be ideal.
400cc 4 stroke should be max cc

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3/19/2018 2:44 PM

FYI...

In AMA amateur competition the 250 class is up to 250cc. Two stroke or four stroke. Been that way for a few years now and the four strokes continue to be winning most of the time.

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3/19/2018 3:36 PM

Jrewing wrote:

Im more concerned with Electric bikes and how they'll regulate that direction.
200cc 2 stroke for the lites class is what I think would be ideal.
400cc 4 stroke should be max cc

This is an excellent point, the horse is already out of the barn in regards to 2T 4T.

I spend a lot of time on different bikes. I feel like HP should be capped somewhere around 45 with the development class, and 55 with the premier class. At the most.

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3/19/2018 7:49 PM

Zoom wrote:

FYI...

In AMA amateur competition the 250 class is up to 250cc. Two stroke or four stroke. Been that way for a few years now and the four strokes continue to be winning most of the time.

What percentage of those 250cc four-stroke racing amateurs pay for their own bikes, mods, and maintenance?

If the parents and/or the OEMs and aftermarket stopped subsidizing amateur four-stroke racing, I'd wager a guess the two-strokes would be winning these amateur 250cc events.

Eventually there won't be enough paying participants to subsidize amateur four-stroke racing. And heaven help us if the energy drink money goes away.




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"Thank God my father wasn't rich."
-Hurricane

"You wouldn't take clay to Southwick, so why take sand to Red Bud?"
-DV

"I ride a two-stroke because I am Weigandt-level cheap"
-Me

3/19/2018 7:56 PM

ga_pike wrote:

175/200 and 300/350 IMO

This

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3/19/2018 7:58 PM

make1go wrote:

Oems got some people in their pocket or it would have been rectified 10 yrs ago..

and now with no japanese engineers driving inovation,
and thus competition.
we have no idea where a 2018 2 t would be in comparison to a 4t...

This also

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3/19/2018 8:00 PM

GuyB wrote:

Huh...I must have missed the part where the AMA "admitted" that. Maybe you can point me in the right direction.

I've read the same thing, they also stated that they under estimated the power that could be produced. But I'm not going to look for the article but I've read something similar also.

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