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rdefonce

2010 YZ450F GYTR flywheel . . . why so light?

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I'm looking at GYTR flywheel for '10 450F's and I notice they are quite a bit LIGHTER than previous years; 4oz vs 9oz . . . can I assume they will have same effect on motor as the heavier ones for previous year bikes??

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Supposedly it isn't just the weight of the flywheel. I would assume that it would have the same effect like you are thinking. But I'm no expert on flywheels.

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Because the 2010 flywheel is larger in diameter, less weight has a greater effect. In the '06-'09, the stock inertia mass is 3.8 kg-cm². Adding 9.21 oz. yeilds an inertia mass of 6.15 kg-cm². The addition of 4.44 oz. on the 2010 yields an inertia mass of 9.5 kg-cm², so it is even more effective.

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Very interesting, thanks Gray for the definitive answer!

(sold my '08, I am about to pull the trigger on a new leftover '10 but want FW weight for this bike)

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Just an FYI, they were backordered when I palced an order mid december. I got mine from motosport and it says call for availability still. Originaly I was supposed to get mine between Jan to Feb but it came christmas eve. I also found it significantly cheaper from another online distributor but can't remember which one at the moment. They were also backorder from them as well. They also come with a new gasket which I didn't see in the writing anywhere so no need to order one.

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Just an FYI, they were backordered when I palced an order mid december. I got mine from motosport and it says call for availability still. Originaly I was supposed to get mine between Jan to Feb but it came christmas eve. I also found it significantly cheaper from another online distributor but can't remember which one at the moment. They were also backorder from them as well. They also come with a new gasket which I didn't see in the writing anywhere so no need to order one.

tech24 thanks for that info. Looks like i better get it ordered before even finding a bike!

I suppose if I ended up not getting a '10 yz I could easily sell it . . .

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I want to make sure I am understanding this correctly. I know the amount of the weight is not as important as the amount of weight and where it is placed on the flywheel (i.e the inertia mass), but the inertia mass that GYTR is showing is pretty substantial.

Here's where I'm confused. For an '09 it shows a stock inertia mass of 3.8 and the GYTR part is 6.15. My thinking is that it is an approx 62% jump in flywheel effect. So for the '10 and up YZ it is approx 54% more flywheel effect than the GYTR unit for the '09 (9.5/6.15)?? If so, that's a huge difference! The site does not show what the stock inertia mass is for the '10, but if it was again 3.8 the heavier flywheel would have something like 2 1/2 times more flywheel effect than the stocker. Is this correct? Has anyone tried one of these yet?

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The site does not show what the stock inertia mass is for the '10, but if it was again 3.8 the heavier flywheel would have something like 2 1/2 times more flywheel effect than the stocker. Is this correct?
No. The stock '10 flywheel is going to have a far greater inertia mass than the stock '09, simply by virtue of its much larger diameter. Even if it weighed the same (which would be impossible from a practical standpoint as small as the '09 is), the '10 is more than 50% larger diameter to begin with. Plus, it carries more magnets, making the outer ring considerably heavier. The larger diameter also increases the effect of any given amount of weight that might be added by an exponential amount.

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No. The stock '10 flywheel is going to have a far greater inertia mass than the stock '09, simply by virtue of its much larger diameter. Even if it weighed the same (which would be impossible from a practical standpoint as small as the '09 is), the '10 is more than 50% larger diameter to begin with. Plus, it carries more magnets, making the outer ring considerably heavier. The larger diameter also increases the effect of any given amount of weight that might be added by an exponential amount.

So I guess it's difficult to say how much more effect it will have over the stock flywheel, but it seems to have a pretty healthy effect over the '09 GYTR part. It's definitely priced like it has a big effect!

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The reason it's so expensive compared to the older ones is because of the extra machine work involved in it. The outer ring of the '10+ is a reluctor (pulse wheel ) for the EFI ECM. Has all those square teeth cut in it.

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