4-stroke's?

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#1
I was just wondering if anyone knew if there would ever be any 4-stroke mini motocross bikes to match up with the 85's..

YZ 170F?
KX 170F?
CRF 170?
RM 170Z?

That would be pretty neat.
 

Jasle

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#2
you'd have to think that eventually there will be. I've heard 2006 is the target for all non-competition bikes to be 4 stroke only. The competition models will follow suit a few years after that I'd bet.
 

nikki

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#4
I think the idea is to have 150cc 4-strokes to compete in the 85cc class sometime in the future.
 

jboomer

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#5
Supposedly Yamaha has one in the wharehouse somewhere, but is waiting to release it when the AMA decides what the displacement ruling will be.
 
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#6
Acually, yamaha already has finished R&D on a yz125F, theres no way it will be 170s or 150s competing against 85 2-smoke machines. Yamaha is just waiting for the rules to change and let four strokes compete in the class. Well see them pretty soon ill bet
 

ACS

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#7
The rules are already in place. The FIM makes the World rules that the rest base theirs on. The class is up to 125cc 4 stroke with the 85's so no 150cc etc unless they again revisit the rule book. The FIM set the limits and thats why we are seeing the upper limit of the big bikes as 450's. The 125 / 250 rule was in the book for years. On the World stage Yamaha used that rule and lucky the AMA let it in to race in USA. Remember a lot of development work happens in Japan and their rules come via the FIM. Think of the Motocross de Nations races, they run FIM rules as do the FIM World MX series were the major companies develop the bikes. The USA is a "dangerous" place to develop bikes in AMA racing as you have a requirement about frame modifications (close to stock) and the old claiming rule.
 

Chili

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#9
Originally posted by Dogman5
That doesent make any sense though.

An CR 85 would own an CRF 150..
Your talking apples and oranges here. By the same standards a CR125 would own an CRF230. If/when they release a 125cc 4 stroke race bike you can bet it will competitive just like the 250F's are now.
 
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#10
Originally posted by Chili


Your talking apples and oranges here. By the same standards a CR125 would own an CRF230. If/when they release a 125cc 4 stroke race bike you can bet it will competitive just like the 250F's are now.
Yeah, but why would it be only a 125cc 4-stroke Motocross bike is what I am saying. Wouldn't a 4-stroke bike have twice the amount of cc's than the 2-stroke? (ie: a YZ 125 is equivelant to a YZ 250F) ?

125cc 4-strokes just wouldnt hold up against 85s at all. I have ridden both a CR85 and a CRF150, and the 85 is alot faster.
 

jboomer

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#11
The CRF 150 is built for play riding, not for serious mx. Just like the XR250 couldn't hold a candle to the CR125 on a racetrack.
 
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#12
Originally posted by Tiylu


Yeah, but why would it be only a 125cc 4-stroke Motocross bike is what I am saying. Wouldn't a 4-stroke bike have twice the amount of cc's than the 2-stroke? (ie: a YZ 125 is equivelant to a YZ 250F) ?

125cc 4-strokes just wouldnt hold up against 85s at all. I have ridden both a CR85 and a CRF150, and the 85 is alot faster.
well then wouldn't 500cc 4-strokes be up against 250 2-strokes? they don't decide that 4-strokes are twice the cc of their respectable 2-stroke counter parts. it's just what they decided. don't get caught all up in the world of displacement guys.....
 

23jayhawk

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#13
I think the key thing is that the power band on a 2T diminishes at an almost geometric rate with displacement; at some point the tractability of a 4T would be enough of an advantage that it could easily be faster for mortal riders, despite being down a couple/three hp.
 
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#14
There isn't a decent 125cc four stroke made yet. All the smaller 4-strokes are 20-30 year old technology.
I can see a 20+ HP 125cc motor with all the latest technology. We'll have to wait and see what they come out with. Imagine a 125cc 4 valve liquid colled lightweight 4-stroke. Man I'm starting to drool!!
Also the torque of a four stroke is MUCH higher than a 2-stroke and thats what really counts.
 
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#15
i think that a 4 stroke race bike would be awesome in the 85 class!!! my mom has a ttr 125 i like how much traction it has it just needs more power!! if they started making a 4 stroke race bike for the 85 class i would definetly switch