WHAT IS IT? The FMF Racing 4.1 HEX RCT exhaust system for the 2018–2022 Suzuki RM-Z450 is designed to save weight and improve power across the entire rpm range. It is also shorter in overall length to make it less susceptible to damage in a crash and to move the muffler closer to the engine in order to centralize mass.  

WHAT’S IT COST? $899.99 (stainless with carbon cab). 

CONTACT? or (310) 631-4363. 

WHAT STANDS OUT? Here’s a list of things that stand out with the FMF Racing 4.1 HEX RCT exhaust system.

(1) HEX. The “HEX” terminology comes from the hexagon-like shape of the muffler’s end cap instead of the standard oval. The hexagon shape was used to work with the updated Hi-Flo internal core structure to increase airflow, power and torque. The stainless steel 4.1 FMF exhaust system featured a carbon fiber end cap for a factory look. The stainless FMF system weighs more than the Ti system, but it is more durable.  

(2) Stock power. It’s no secret that the Suzuki RM-Z450 has been growing long in the tooth for some time now. The last update came in 2018 when Suzuki updated its chassis, but Suzuki left the 8-year-old engine unchanged. Despite its age, the RM-Z450 engine isn’t horrible. The low-to-mid is where this engine shines. It rewards those who short-shift and keep the revs below 8800 rpm. Make no mistake, the RM-Z450 will rev to 11,000 rpm, but after 8700 rpm, the power starts to fall flat. Although the low-to-mid range is good on this bike, it still feels like something is missing. Test riders had to rely heavily on the clutch to get the bike moving in some of the tighter corners on the track.     

(3) Performance. Immediately after installing the FMF system and starting the bike, we noticed a massive difference in throttle response, and we hadn’t even taken the bike off the stand yet. With the stock Suzuki RM-Z450 being down on power to the tune of 4 horsepower to its competition, aftermarket parts tend to make a bigger difference on this bike compared to some of the other brands, so we were excited to race it. On the track, test riders were pleased that the throttle response heard when the bike was on the stand transferred over to the dirt. With the FMF system, test riders noticed a more connected feel between their right wrist and the rear wheel. Although the FMF system didn’t do anything to the top-end power of the RM-Z450, test riders were happy that it added more to the RM-Z450’s low-to-mid meat of the powerband, allowing them to rely less on the clutch in tighter corners. Even with the added power, it was still an easy-to-ride powerband that didn’t wear us out over long motos.  


(4) Weight. The FMF 4.1 HEX RCT RM-Z450 exhaust system is 3 inches shorter than the stock system, which brought the total weight loss to 2 pounds over the stock system.    

(5) Fitment. We have to give it to the engineers at FMF; this system was one of the easiest to install. All the bolts lined up without a hitch, and no T-handles were thrown across the garage during the installation process.   

WHAT’S THE SQUAWK? The stock RM-Z450 muffler is rubber-mounted; the FMF muffler is not. You will need a shorter bolt to secure the FMF muffler to avoid the bolt going through the backside of your rear fender.  

MXA RATING: The FMF Racing 4.1 HEX RCT system brought our RM-Z450 to life. The improved throttle response and melodic sound garnered positive reviews from MXA test riders of all skill levels. Getting rid of the ugly stock system was also a plus.

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