Did you know that the 2026 Yamaha YZ450F comes standard with a heavier flywheel (over the 2025). With that being said we did go to an aftermarket heavier flywheel weight in 2025 (Bundy Built Flywheel) for better control of the power, so we decided to try all of the different sizes/options while we were in Georgia and wanted to give you some feedback. Below is a rundown of how each weight performed as well as weights and inertia numbers.
2025 Flywheel: 434.9 (g) Inertia (g*cm2) 6.0
We used this weight as a baseline for others as a comparison.
2026 Flywheel: 456.9 (g) Inertia (g*cm2) 6.5 (Increase over 2025 is 8%)
If you’re looking for that quicker spool up of the 2025 and want some added excitement from lower RPM situations, the 2025 flywheel will work well for bigger riders or guys who want a quicker recovery in softer dirt. The 2026 flywheel along with the other changes Yamaha made to the bike has more engine braking than that of the 2025. Normally going to a heavier flywheel can create less engine braking but with the modifications Yamaha made to the engine/intake of the 2026, I felt more engine braking with the 2026 flywheel weight. However, the control you get out of corners with this flywheel size is best for me in almost all conditions. In soft Georgia dirt as well as Glen Helen type dirt, this new flywheel weight worked well. If you want to use this flywheel weight and get less engine braking, going to a different Yamaha Power Tuner map is a must. Below is a more FREE FEELING map that I liked better in east coast dirt.
GYTR Optional Flywheel 509.9 (g) Inertia (g*cm2) 7.8 (Increase over 2025 is 30% and 20% over 2026)
This is a good option if you’re looking for a little more “chugging” in higher gears and more lugability from the 2026 engine. Yes, you still have about the same amount of engine braking of the 2026 flywheel but you’ll have some added torque feeling through 2nd-3rd gear. The engine will be slower to rev which can help rear wheel traction. I do think this is too much weight for a deep (east coast) style mx track that needs more response or quick rev low RPM feel. This flywheel might be a little too lazy feeling for that those type conditions. I do like this option with 2025 intake and aftermarket muffler. With those mods this flywheel helps rear traction and prevents some of that on/off feel that the 2025 YZ450F can have at low RPMS (think rolling throttle on through shallow ruts). Retail price for this option is $254.99 and will fit 2023-2026 YZ450F, 2024-2026 YZ450FX and 2024-2026 WR450F. Yamaha Part Number D03-H13A0-V0-00
Bundy Built Flywheel 514.9 (g) Inertia (g*cm2) 7.9
*Similar feel to GYTR option* Going to the Bundy Built flywheel creates similar feelings to me on the track as the GYTR version but you will have to send your flywheel into Bundy Built versus buying a complete flywheel w/ wight like GYTR offers.
