Factory 4.1 SL – Stainless Steel (S/S) Midpipe
Titanium slip-on muffler with stainless steel midpipe. Available in natural titanium or blue anodized finish. Fits stock or FMF header. - Boosts low-mid torque, broader powerband, more over-rev.

- Features exclusive proprietary Chamber Core technology.
- Factory Forward Engineering centralizes mass, improves handling.
- All titanium construction - canister and endcaps; choice of mid-pipe.
- Made from premium quality American materials.
- Customize with performance tuning inserts and spark arrestor module.
- Meets AMA sound requirements on most models; inserts available for others. 

The original and still best bang for the buck - the PowerCore 4 S/A.  This is a race design muffler at a value price.  It features our exclusive Hi-Flo square core to evacuate exhaust better and provide maximum core surface area for sound absorption.  The Hi-Flo technology is evident in the stainless steel formed endcaps as well.  For maximum tunability, the PowerCore 4 for a number of applications has a highly versatile modular rear endcap for optional performance accessories – a 2” or 1-3/4” endcap for smoother power delivery, a quiet core insert for the sound conscientious and a replacement spark arrestor screen. Some applications feature a fixed endcap and do not allow for optional performance accessories or a quiet core insert. For further information please contact our Customer Service Representatives by phone.  Performance, versatility and pounds lighter than stock – all for an affordable price, FMF’s PowerCore 4…FEEL THE POWER!

Derived from our innovative PowerBomb technology, the MegaBomb represents the natural evolution of our philosophy on performance – improve on it, make it better. What started as a PowerBomb just kept growing. Simply put, the bigger we made it, the better it worked. The engineering wasn’t that simple, we had to fine tune the internal characteristics and there was an upper limit to what was feasible for performance as well as function, but through arduous testing, here you have it! The very same header you’ve seen on the Factory KTM and Yamaha of Troy bikes as well as Team Suzuki Off-Road and that of Ryan Hughes. This is not ‘Un-obtainium’. The MegaBomb ships right out of our warehouse to you just as it would to any race team or magazine. What makes a MegaBomb so different? There are two key aspects. First, the more exhaust gases that are extracted, the better. Like the difference between a garden hose and a fire hose – except, too much is not good. The calculated size of the MegaBomb chamber, with the precise location and size of internal ducts, makes for increased volume. The second aspect is the performance difference between a short header, better over-rev, and a long header, better low-end torque. With the MegaBomb, you get the best of both. The added volume acts like a long header and the length has not been increased. Here’s the bottom line. You want better performance. You can pay an engine builder thousands to make more power or bolt on a MegaBomb for more useable power from the stock motor as well as a 3-5hp boost! Take your pick. As an added benefit, you will also have a lower sound output by up to 1.5dB. For three hundred and fifty bucks, the answer is obvious. Choose FMF and FEEL THE POWER!

- Increases output from stock motor as much as 5hp.
- Produces long header torque and short header over-rev.
- Reduces sound output as much as 1.5dB.
- Made from premium Ti-Metal^® American material.
- Patent pending technology.

The redesigned PowerBomb is a four-stroke header that incorporates FMF's patented PowerBomb module at a precise location in the initial stage of the header. By positioning this "Bomb" at a key point in the system, increased performance and flow is achieved through the expansion and contraction of exhaust sonics through the system. Result is a flow increase of nearly 10%! The outer chamber in the Powerbomb allows the air to expand, cool and ramp back up at a higher velocity.

Additionally, the PowerBomb is a "pre-muffler" of sorts which helps to lower the bikes sound output by providing more sound absorbing surface area for the sound medium (exhaust gases). On some models, you can choose between a moto or supercross version. The supercross version is designed for more low to mid-range power where the moto version is focused in the mid to upper RPM range.