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Steve Buckner
Joined: 22 Apr 2003
Posts: 839
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 Posted: Thu Oct 04, 2012 9:15 am Post subject: |
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| Chris Reinhardt wrote: | | Spencer Uzri wrote: | Lest we forget, the AMA rules mean 4's have a power advantage by virtue of their larger displacement. I would've liked to see an EXP-2 style 125cc EFI engine compete with a modern 4-stroke, but Honda has made sure that will never happen.
That said, I will be watching to see how well these new 4's hold up in a kart application. If they have the valve-throwing problem eliminated, then my curiosity will be piqued. |
You mean least we forget? Spencer, I think you need to re-read your 2 stroke and 4 stroke engine theory????
From AMA Pro Motocross Rulebook:
3.1 Engine Displacements
a. 250 Motocross Class:0 – 125cc 2-Stroke / 150 – 250cc 4-stroke
b. 450 Motocross Class:150 – 250cc 2-Stroke / 251 – 450cc 4-stroke |
Are 125cc 2 stroke and 250cc 4 stroke / 250cc 2 stroke and 450cc 4 stroke the same displacements for each class. |
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Spencer Uzri
Joined: 18 Apr 2006
Posts: 798
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| Posted: Thu Oct 04, 2012 11:51 am Post subject: |
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| Chris Reinhardt wrote: |
You mean least we forget? Spencer, I think you need to re-read your 2 stroke and 4 stroke engine theory????
From AMA Pro Motocross Rulebook:
3.1 Engine Displacements
a. 250 Motocross Class:0 – 125cc 2-Stroke / 150 – 250cc 4-stroke
b. 450 Motocross Class:150 – 250cc 2-Stroke / 251 – 450cc 4-stroke
How are any 2 strokes eliminated?
All the reliability bugs have been worked out of the 4 strokes except one.... Lack of maintenance, it will kill a 4 stroke quicker than a 2....
CR |
I'm aware the rules allow close - but not equal - displacements between both types to run together in a class, but how often do you see that actually occurring? Every time I catch an AMA MX race with mixed engine types, it's always 125 (2) v 250 (4) & 250 (2) v. 450 (4). Guess why?
Once again, I have no issue with the engine. EFI is an improvement. I'm still concerned about the potential of a thrown valve, but time will tell if that has been remedied. If it has, then it may become the shifter class motor to have. The only other obstacle, then, will be price point.
Last edited by Spencer Uzri on Fri Oct 12, 2012 8:00 am, edited 2 times in total |
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Steve Buckner
Joined: 22 Apr 2003
Posts: 839
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| Posted: Thu Oct 04, 2012 7:24 pm Post subject: |
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Now a 465 or 490 yamaha two stroke would be a good match. Damm those where fast bikes. Brad Lackeys Kawasaki sr 500 was one fast mofo also.
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Christiaan Bouhuys
Joined: 03 Jun 2010
Posts: 97
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Jim McMahon
Joined: 07 Apr 2007
Posts: 2658
Location: United States, St. Paul,
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| Posted: Fri Oct 12, 2012 10:07 am Post subject: |
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Heavy?!? It's 16KG 34lbs. Granted it might be a bit more "top heavy" with the valvetrain but at 16KG and 38HP it rivals some of the late Formula Super A motors! Rotax DSD was 15KG. Granted you have a rad and exhaust to add to weight but still, all things considered its hardly a sled. Still a lighter package than any shifter.
_________________
GPI Racing | WildKart | Maxter | Hoosier
Karting Festival @ Blackhawk Farms June 1st-2nd. |
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Christiaan Bouhuys
Joined: 03 Jun 2010
Posts: 97
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| Posted: Fri Oct 12, 2012 10:36 am Post subject: |
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| Jim McMahon wrote: | | Heavy?!? It's 16KG 34lbs. Granted it might be a bit more "top heavy" with the valvetrain but at 16KG and 38HP it rivals some of the late Formula Super A motors! Rotax DSD was 15KG. Granted you have a rad and exhaust to add to weight but still, all things considered its hardly a sled. Still a lighter package than any shifter. |
It looks really heavy...and in the wrong place...compared to another Vortex single-speed engine (RAD), which weighs 10kg, has more power and a better weight distribution. Ah well, I actually don't care about the facts. It just looks heavy, will likely sound bad, and it does not produce the smell and smoke I like. |
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