flywheel 14, 12, 10 oz. whats the difference?

hey all whats best for me? i have an 03' yz450f and want a heavier flywheel to stop stalling. what brand should i go with? i have stock jets, should i change them too? i only do trail riding with some tight trials mixed in. thanks in advance for any help what so ever.


the weight will slow or soften the hit of the motor .you dont need to rejet and the heavier the weight the more effect it has on the hit .drd is supposed to be a good one as well as gytr.

Since we are on the subject and I know that it has been discussed before, I am wondering if anyone has used the "lighter" GYTR flywheel on an 04 450F. If so, can anyone share some information on what it did to the power characteristics of the bike. Like Keitzn, I am also looking to install a heavier flywheel but not looking to go any heavier than 6oz as the bike is used for track use only.


First, understand that there are two different approaches to adding flywheel weight, bolt-on weights, and flywheels with weight added.

The biggest difference between these is that the weighted flywheels get more flywheel effect for less added weight simply because the entire added mass is on the outer circumference of the flywheel. The center hub of a bolt on accounts for 3-5 ounces of its weight and doesn't do much for the bike because it's too close to the shaft center to add much inertia. Thus, a 6oz Dr.D is about the equivalent of a 10oz bolt on. The really interesting thing to me is that they both cost about the same, which, IMO, makes the bolt-on weights something of a rip-off. The bolt-ons are only more complicated to make because they need holes drilled in them, and the welded-on types are dynamically balanced once finished. Furthermore, welded weights never work loose.

Dubach Racing Development sells theirs on an exchange basis, and they will send you your new one before you send them your old one, taking a core deposit on your credit card temporarily. They will also exchange for a different weight anytime, charging only for shipping, even if you aren't the original purchaser. His are available in 4, 6, and 8oz over stock. Doug's cool.

I use the lighter of the two GYT-R weights on my '03. According to Dubach, they GYT-R flywheels are about 5 & 7.5 oz heavier than stock. The fact that Yamaha rates theirs in terms of inertia mass makes it hard to compare them without knowing that. It was an improvement over the Dr.D 4oz I had already, but it was hard to notice except for the fact that in some places where a handful of throttle used to break the tire way loose, the bike now raises the front wheel and bolts. That's the real difference; traction. Compared to the stock flywheel, either is a massive improvement in controllability. My opinion is that the 4oz is not enough weight, at least for the '03, and I would recommend the light GYT-R or the 6oz Dr.D for MX. Heavier, if you want, for trails only kind of stuff.

I found the GYT-R flywheel for sale used, and I still have the Dr.D 4oz, so what I plan to do is swap it for an 8oz and switch between them when the circumstances call for it. They're easy to change out with the right puller.

As far as jetting, none is required. A heavier flywheel has the same effect on an engine as mounting a tire on a wheel does. Without the tire, the wheel is easily spun by hand from a standstill, and easily stopped with a couple of fingers. But with a big ol' knobby on it, it's much harder to do either. The same with your engine. As it comes, it accelerates its own mass so easily that it also has no trouble spinning up everything connected to it, rear wheel included. Conversely, it has so little inertia that the brake can easily stall the engine. But if you make the rotating mass of the crank a little heavier, the engine has a little more work to do as it tries to accelerate, which helps the tire maintain its grip, and it's a little harder to stop the crank by mistake in the bargain.

A heavier flywheel does not reduce the power output of an engine, and in most cases won't change the top speed at all (in really small engines, it can even increase the top end a little), it just changes how suddenly it can change speed. The difference in acceleration is only apparent in the lower gears, and in third and fourth, you wouldn't really know which of two otherwise identical bikes was stock, and which had a 6oz flywheel.

thanks a bunch for all your help garyracer513. i prolly should have mentioned before that i have an 03' yz450f motor in an 89' honda 250r frame w/ all other componets being honda. its got everything i want on it and im just tring to get the motor perfect too.

right now i have a full system curtis sparks exhaust from the 450 quad on it w/ a K&N air filter. the filter has a outerwears cover and the air box lid has 6 1/2 holes drilled in it for the only ventilation. the jetting is stock right now. ill prolly go with the 7.5 gyt-r flywheel.

1. should i change jetting?

2. should i change sprockets? right now i have a 14/38 set up and my front end likes to lift. i want to shift more on tight trails also and get out of first. any ideas?

thanks in advance as always. you guys rock and keep my rollin.


Thanks for the information grayracer.

As you mentioned, with GYTR designating their flywheels by intertia mass, I too was having porblems figuring out how much weight it actually added. I figured that the "lighter" GYTR part would fall somewhere in between the Dubach 4oz and 6oz based off of some information I saw on Yamaha's website as well as Doug's. Hopefully, that is correct... Do you have any suggestions on removing the old one and installing the new one?


Hopefully, that is correct... Do you have any suggestions on removing the old one and installing the new one?


I asked them; it is. My suggestion is to spend the $14 or less it takes to but the right puller (the one for the YZ fits so many bikes I'm surprised they don't have them at the grocery store) and make your life easier. If once you get what you think is an adequate amount of pressure on the puller it still hasn't popped free, try cracking the end of the puller pressure screw sharply with a hammer. Hold onto the flywheel; it will bounce right off.

Thanks again for the information Grayracer.

Just out of curiousity, where did you get your flywheel puller?

I saw that ZIP-TY racing has one for about $15.00. Any other

suggestions? Also, what did you use to hold the flywheel in place

when you went to loosen and tighted the large nut that holds the

flywheel in place?


.... Or what's the best way to lock the flywheel when torquing it on? If it moves at all, you cannot get an accurate torque reading - so looks like I am getting the tool from Yamaha to hold it. Got it off OK by putting the bike in high gear, activating the rear break and tapping the wrench with my hand to break it free..

BTW.. I am finishing up the install of a 10oz Stealy flywheel weight on my 02 426.. Not a huge job but required the purchase of a drill press as you have to drill and tap holes in your stock flywheel.. Need to get the holes right. Let you know how the bike behaves once I get it done and ride it..



You can get universal tools like the flywheel holder from Sears, or a number of other outlets. Another option is a strap wrench (carefully). There isn't a reason why your torque reading won't be accurate using the brake or blocked wheel method.

As for where to get a puller, take a look at This Listing (half way down) and see how many bikes the P515 fits. You should be able to find one almost anywhere without ordering it. If you go with a Dr.D flywheel, he sells the pullers too.

Thanks a lot for the help and the information.

I'm going to see if I can find the flywheel puller locally....

Thanks again.

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