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wondermuscle

GYTR Off-Road Flywheel Ride Report '06 - '09

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I bought a YZ for single track and desert racing in Southern California, this is my first MX bike as I have only had WR types before. I rode it several times and found that I was stalling it much more often than my other bikes. So I bought the GYTR Off-Road Flywheel.

GYT-2S297-50-50 adds 9.21 oz for an inertia mass of 6.15kg-cm^2, twice the stock inertia mass of 3.8 kg-cm^2. This is only for 2006-2009 450’s.

http://www.yamaha-motor.com/sport/products/modelscitemdetail/5/209/1218/5375/2008/1/4335/0/1/detail.aspx

The Heavier Flywheel (HFW) looks like the stocker with an extra ring welding to it as you can see from the fairly representative pictures on the Yamaha -motor website above.

The installation was easy as expected. The hardest part was getting to a local shop to borrow the puller. FYI a CRF puller and new gen Yamaha flywheel use the same puller.

I went to one of my test sites to give the new HFW a test. I was pleasantly surprised how much the HFW helped prevent stalling in the tight stuff. The bike was much less prone to stall and had much more of a tractor feel in the tight stuff without sacrificing the nimble feel of the bike. The throttle was easier to control at very light openings which allowed for better traction in loose rocky terrain and hill climbs. It made riding in the tight stuff much easier and more fun. Thankfully it did not affect the midrange hit and hinder the ability of the motor to rev quickly. I think it still revs better than a WR but has the same ability or ride it just off idle without a problem. :banghead:

IMO this is a must have for your YZ in tight trails. :banghead:

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I bought a YZ for single track and desert racing in Southern California, this is my first MX bike as I have only had WR types before. I rode it several times and found that I was stalling it much more often than my other bikes. So I bought the GYTR Off-Road Flywheel.

GYT-2S297-50-50 adds 9.21 oz for an inertia mass of 6.15kg-cm^2, twice the stock inertia mass of 3.8 kg-cm^2. This is only for 2006-2009 450’s.

http://www.yamaha-motor.com/sport/products/modelscitemdetail/5/209/1218/5375/2008/1/4335/0/1/detail.aspx

The Heavier Flywheel (HFW) looks like the stocker with an extra ring welding to it as you can see from the fairly representative pictures on the Yamaha -motor website above.

The installation was easy as expected. The hardest part was getting to a local shop to borrow the puller. FYI a CRF puller and new gen Yamaha flywheel use the same puller.

I went to one of my test sites to give the new HFW a test. I was pleasantly surprised how much the HFW helped prevent stalling in the tight stuff. The bike was much less prone to stall and had much more of a tractor feel in the tight stuff without sacrificing the nimble feel of the bike. The throttle was easier to control at very light openings which allowed for better traction in loose rocky terrain and hill climbs. It made riding in the tight stuff much easier and more fun. Thankfully it did not affect the midrange hit and hinder the ability of the motor to rev quickly. I think it still revs better than a WR but has the same ability or ride it just off idle without a problem. :banghead:

IMO this is a must have for your YZ in tight trails. :banghead:

Nice write up. The puller info is handy to know, as well as how the bike tracks.

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Yes, I Agree. If you ride offroad it is a must have.

I found my 06YZ450 ripped my arms off on the trail without it and I tired much quicker.

With it installed it was a smoother power delivery and I can almost idle in first gear through the rocks.

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I installed one of these on my own '06 quite a while ago, and IMO, the bike should have been built with it. It makes the engine pull more smoothly at lower engine speeds, and frankly, it pulls harder below 4000 than it did without the added weight. There is also no detectable downside in terms of power, acceleration, or any other noticeable or measurable attribute. Mine pulls dead even through the gears with my son's bike which is otherwise identical.

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I'm happy with mine also, though I still have stalling issues in really tight riding. What gearing are you running?

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I'm happy with mine also, though I still have stalling issues in really tight riding. What gearing are you running?

I run 14/50 tops out about 83mph

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I'm happy with mine also, though I still have stalling issues in really tight riding. What gearing are you running?

I run both 14/46 for desert and 13/48 for single track. It behaves better with both setups. It is harder to stall.

Like Gray said it pulls harder down low. Once that added weight begins to accelerate from the initial hit, you really feel it down low. The bike feels more torqueie.

Can't wait to ride! :banghead:

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I run a 13/48 on my '06.

The reason the flywheel actually increases very low rpm power goes to what the whole purpose of a flywheel on any engine is in the first place. Engines don't run at a steady speed while operating slowly. They accelerate when they fire, and then slow down as they coast to the next compression stroke. The fewer cylinders you have, the more this is true. The amount of speed lost between power strokes is energy that has to be regenerated just to break even.

Engines, then, must be built with enough rotating inertia to at least keep them running, and in the case of the YZ450, that's really just about all it has. Adding weight to the crank reduces the amount of energy loss between power strokes at low speed by storing it as inertia, so that not so much of it has to be made up for. This is only a small amount of torque in reality, but you can feel the difference.

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Gray thanks for explaining it the way you did. I understood the concept but couldn’t visualize it.

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I run both 14/46 for desert and 13/48 for single track. It behaves better with both setups. It is harder to stall.

Like Gray said it pulls harder down low. Once that added weight begins to accelerate from the initial hit, you really feel it down low. The bike feels more torqueie.

Can't wait to ride! :banghead:

Good info, I'll have to try a 13/48 or 49 and see how much difference it makes. Still stock gearing on my bike BTW.

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Yes, I Agree. If you ride offroad it is a must have.

as opposed to riding on road?

:banghead:

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as opposed to riding on road?

:banghead:

No, as opposed to riding MX....... Mx and off road are a bit different there buddy. :banghead:

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One aspect of flywheel weights I haven't seen discussed much is the increased gyroscopic force. For those of you that haven't had the opportunity to play with a gyroscope...this is the force from a spinning mass that resists change of motion (my backyard definition). For example on a motorcyle this would resist the bike turning a corner. I have heard it speculated that this is the reason some of the big bore bikes feel heavier than they are (relative to smaller bore bikes).

I have a bike with a heavy FWW on it, and overall I like it but I can't honestly say if there was an effect to the cornering because I haven't switched back and forth so now I have nothing to compare it to.

Anyone adding a FWW notice the bike feels heavier in the corners?

The fact that you can lug it more and are at lower rpms, may at least partially compensate...

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