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124cc? 249cc? 449cc? Why??????

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Okay it's finally gotten to me... why do all the manufacturers (sp?) make their 'actual' sizes like this? Why can't they just make the 125, 250, 450 etc.??

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I believe it's due to racing classes. That's why a 250 cc can run in a 125cc class. Because it's less than 250 cc. Smart huh?

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Okay it's finally gotten to me... why do all the manufacturers (sp?) make their 'actual' sizes like this? Why can't they just make the 125, 250, 450 etc.??

I believe those are the displacement limits in the classes and they must be under them. Correct me if I'm wrong though

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I believe it's due to racing classes. That's why a 250 cc can run in a 125cc class. Because it's less than 250 cc. Smart huh?

Are you talking about a 4 stroke 250? Because I believe the AMA rules say that a 4 stroke can have twoce the displacement limit because they are so down on power.

I believe those are the displacement limits in the classes and they must be under them. Correct me if I'm wrong though

Thats what Ive always thought.

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i dont know. every now and then i see like 248 or 249.3. im not sure why no one makes it exactly 250 and 450, but all i know is no one does so there must be a reason

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I would think its to leave a little tolerance. If they say the cc is exactly 250 and someone at a race actually checks the displacement and it comes back 250.0001, thats an illegal bike. But if the limit is 250 and the displacement is 249, there is room for that error. Nothing is perfect.

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Okay it's finally gotten to me... why do all the manufacturers (sp?) make their 'actual' sizes like this? Why can't they just make the 125, 250, 450 etc.??
Easy, they get as close at they can without going over. Do some math, to figure dispalcement, use this formula.

.7854 X bore X bore X stroke X# of cylinders.

Lets say we have a 95mm bore X 63.4 mm stroke (this is the WR450F specs) (this is also known as a "oversquare" when bore and stroke are the same, its "square" and undersquare when bore is less than the stroke. Now convert the cubic millimeters cubic centeimeters by moving the decimal 3 places to the left and round off, in this case, your 449 cc again.

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Easy, they get as close at they can without going over. Do some math, to figure dispalcement, use this formula.

.7854 X bore X bore X stroke X# of cylinders.

Lets say we have a 95mm bore X 63.4 mm stroke (this is the WR450F specs) (this is also known as a "oversquare" when bore and stroke are the same, its "square" and undersquare when bore is greater than the stroke. Now convert the cubic millimeters cubic centeimeters by moving the decimal 3 places to the left and round off, in this case, your 449 cc again.

Exactly , and it also leaves a little room for honing and boring.

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