2010 GYTR flywheel for MX

I've searched and read tons of posts about how the 2010 YZ450F benefits from the GYTR flywheel weight off road, but what about at the MX track? Any MX-only guys using it? If so, how has it affected the the way it runs at the track (not just stalling, but overall performance)?

The flywheel itself on the '10+ is heavier to begin with than that of the '06, but I don't know if the '10 crank is lighter, so I don't know for sure that a direct comparison can be drawn safely, but the heavy off-road flywheel on the '06-'09 does nothing but good for the bike. It pulls stronger at low speeds, and suffers no loss whatsoever in acceleration through the rev range. Traction improves a bit, too.

I have always liked the effect of a heavier rotating mass in an dirt bike engine. I remember that when I was racing CZ 380's, it was popular as a hop up to use an aftermarket electronic ignition with a relatively tiny rotor. This was a good idea on the 250 CZ, but most people who tried it on the 380 went back to the big factory flywheel because the bike was more controllable, and their lap times went down.

I think the same thing in general applies to the YZ450. They tend to be a bit snappy and hard to manage, and the increase in weight helps. Again, this may not directly apply to the '10, but I would not be at all surprised if it did.

I really like the powerband and the tunability with the tuner. However, as a novice, a little more control on corner exit, and traction or torquey pull on straights would help. I just don't want to hurt it's ability to build revs out if a corner before a jump face.

... I just don't want to hurt it's ability to build revs out if a corner before a jump face.
I honestly don't think you'll notice a difference in that regard.
The flywheel itself on the '10+ is heavier to begin with than that of the '06, but I don't know if the '10 crank is lighter, so I don't know for sure that a direct comparison can be drawn safely, but the heavy off-road flywheel on the '06-'09 does nothing but good for the bike. It pulls stronger at low speeds, and suffers no loss whatsoever in acceleration through the rev range. Traction improves a bit, too.

I have always liked the effect of a heavier rotating mass in an dirt bike engine. I remember that when I was racing CZ 380's, it was popular as a hop up to use an aftermarket electronic ignition with a relatively tiny rotor. This was a good idea on the 250 CZ, but most people who tried it on the 380 went back to the big factory flywheel because the bike was more controllable, and their lap times went down.

I think the same thing in general applies to the YZ450. They tend to be a bit snappy and hard to manage, and the increase in weight helps. Again, this may not directly apply to the '10, but I would not be at all surprised if it did.

And finally an admission that the flywheel takes away the snap! That is why I do not like a flywheel on my 09. Thank you for the clarification .

And finally an admission that the flywheel takes away the snap! That is why I do not like a flywheel on my 09. Thank you for the clarification .

The snap, yes, a little. The acceleration and or speed, no. If anything, adding rotating inertia improves that in the YZ450. It's a lot like the comparison of the '03 YZF to the '06. Everyone swore the '03 was stronger and that the '06 was soft and gutless by comparison. Trouble is that in any straight line pull on any surface, the '06 is both quicker and faster. My son's '06 and mine were always a virtual dead even match when they were both stock (except for the DRD pipe on both). I put the off-road flywheel on mine, and ever since then mine will pull his very slightly. Explain that.

I know this is one of your 3 core issues, and you can believe whatever you like. You can also set your bike up any way you'd like to. But you're cutting against the grain on this one, I'm afraid.

I was bashed over and over by many with you heading the charge by saying a heavy flywheel does not effect the snap. You now contradicted yourself and stated what I have said and stood by from the start. A heavy flywheel effects the snap, period!

I like the ability to be able to twist the throttle and have the snap without a lag or lethargic feeling right off idle. The 09 in stock form is horrible in my opinion. The addition of the 06 cdi and a Dr D pipe makes it just about perfect.

I didn't mean to start a debate, or rekindle one. However, I do agree. On my 07 KTM 450, I use two flywheels--one for racing and one for trails. The heavier one does take away snap, which makes it great for goat trails. I actually run the lighter one for any racing, even hare and hounds.

The difference is carbs versus FI. I don't care how well jetted your bike is, there is a throttle lag you don't notice until you spend time on an FI bike (at least with YZ and CR). The FI bikes are like a drill motors. Because of the difference in inititial delivery, I think the heavier flywheel effect may provide the benefits without dulling snap as much. I know how they effect carbed bikes, but the FI is a different animal. That's why I posted the inquiry for moto specific use. I do appreciate everyone's input.

Edited by jk322
Not done
I didn't mean to start a debate, or rekindle one. However, I do agree. On my 07 KTM 450, I use two flywheels--one for racing and one for trails. The heavier one does take away snap, ...
The KTM is not a YZ450, and that bike has a greater amount of rotating mass to start with, so they can't really be directly compared.

There's a difference between taking the snap away from a sharp, responsive, well balanced engine and making it lazier and taking the edge off one that's too responsive, too snappy, and is more likely to generate excessive wheel spin as the throttle is opened coming out of a slow corner. The YZ450 is built with too little rotating inertia, in my opinion, and that of a good many others. The bike just runs better with more weight.

As far as not liking the feel of it, I've already proved that most people can't really tell. I installed one on my son's bike without telling him, and he never complained. In fact, about 2/3 through the day, we were taking a break and he said, "the bike's really running good today". I asked him what he meant, and he couldn't describe it. "It just feels good. I don't know."

But again, I don't know how this applies to the '10 and up. You'd just have to try it.

This is an easy one: What is faster traction or wheel spin? Hmmm not sure you take a guess. And if you can feel the difference in the rate the engine RPMs increase you will most likely be the only one on the planet and full of it.

The 2010 is known to have a very little rotating mass and a non existant flywheel effect, very noticable when an aggressive fuel/ign map is loaded in the ecu. In combination with an overly sensitive throttle body setup (unless altered) equals little traction and less control. The bike signs off early anyhow so how would slightly less "snap" hurt performance?

To put in in perspective the bike starves for traction in my opion and anything you can do gain some will make this bike fly. Now I'm more of an offroad rider but I tuned mine to be a dog, added a flywheel, a rekluse, and the slowest opening G2 throttle cam available. Last weekend I tractored up the nastiest, slippery, muddy, rutted, root infested hill that I have ever seen. A lesser bike would have had to have been walked. I'm not very good at MX but it has definently enabled me to corner faster and clear jumps much easier. YOU WONT BE DIAPOINTED!

I think it was Gray that once said there are some top professionals who prefer a heavier flywheel. If some top dogs use it, it obviously doesn't reduce performance to the point where it slows them down. I have a heavier flywheel on my bike and have no complaints other than the fact that it stalls less..

Unless the track is perfectly watered and I'm feeling in perfect shape with great throttle control, a flywheel can be found on my Yamaha.

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