4.1 - Keefer, Inc. Tested

FMF 4.1 Stainless Muffler System (2023 Kawasaki KX250)

The Kawasaki KX250 has undergone some significant engine changes for 2023 and that sparked FMF to make an update to their 4.1 muffler system. The 2023 Kawasaki KX250 engine character has more low end grunt as well as pulling power than last year’s model but it still isn't quite as good as the Yamaha in…

ByKris KeeferDecember 1, 20220Comments

Bolt-Ons Exhaust Hard Parts Husqvarna

To Slip On Or Not To Slip On? FMF 4.1 Slip On Muffler (2023 Husqvarna FC350)

Some muffler questions that get sent to my email inbox usually look like, “which muffler is best for my bike? Is a full system worth the money or can I just get away with purchasing a slip on”? “Is my stock muffler the best muffler option for me”? Instead of trying to keep answering some…

ByKris KeeferSeptember 28, 20220Comments

Bike Brands Bolt-Ons Exhaust KiT Performance Yamaha

FMF 4.1 RCT Stainless Muffler System For 2020 YZ250F

Written/Tested By: Michael Allen It’s no secret that the YZ250F is one of, if not the best 250F in the class for 2020. One of the things that makes the YZ stand out is the raw amount of torque it produces compared to the other bikes in the class. Some of the other bikes may…

ByMichael AllenDecember 16, 20190Comments

Bike Brands Bolt-Ons Exhaust Kawasaki KiT Performance

FMF 4.1 RCT Muffler With SX Style Megabomb Headpipe (2020 KX450)

The Kawasaki KX450 was the most improved 450 machine of 2019 and with Kawasaki not changing anything on the 2020 KX450, I wanted to test some new aftermarket parts to see if I could improve on what I already knew from last year’s machine. I knew FMF had two headpipes available for the KX450, but…

ByKris KeeferAugust 28, 20190Comments

Bike Brands Bolt-Ons Exhaust KiT Performance Yamaha

FMF Factory 4.1 Slip-On (2019 Yamaha YZ450FX)

Story By: Michael Allen The simple fact that more manufacturers are offering off-road closed course competition bike’s brings a smile to my face since at heart I’m an off-road lover. That being said I feel like most manufacturers should know that 99% of all off-road racing organizations require race bikes to be equipped with a…

ByMichael AllenFebruary 14, 20190Comments

Bike Brands Bolt-Ons Exhaust Kawasaki KiT Performance

FMF 4.1 RCT Titanium Muffler System (2019 Kawasaki KX450)

The 2019 Kawasaki KX450 is the most improved machine of the new year, hands down! It has a very responsive engine character, comfortable suspension, a lightweight feel and cornering that is very neutral. I will be the first one to admit that I get nervous about sticking on any type of aftermarket muffler system when…

ByKris KeeferAugust 14, 20180Comments

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