In our FMF YZ450F project in the June issue, the MegaBomb header arrived literally two days after the story was complete. But we finally got it and tested it, so now we can give you that installment.The MegaBomb header has a works look on a four-stroke. Internally there are a few holes inside the mini expansion chamber that give unstable exhaust gasses a place to be absorbed. Another side benefit of this design is a reduction in sound output, up to two db quieter in some cases. On the bike the MegaBomb works as advertised and has the similar effect on the power—a smooth, more-crisp throttle response—but over a wider RPM range. Where the PowerBomb is subtle, you really notice the MegaBomb. Hand-formed, therefore much harder to produce, it retails for $349.99 and has found a home on our YZ450F.
For the full story on our YZ450F motor tuning tweaks from FMF pick up a June Issue of Dirt Rider on newsstands now.