5 of the best 4 stroke exhausts for Enduro & Motocross

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There is much more to 4 stroke dirt bike exhausts than meets the eye. Nowadays, the best 4 stroke dirt bike exhaust systems can not only increase power and look gorgeous but can pinpoint whether power is increased in the low, mid, or top end of the engine’s rev range.
best 4 stroke dirt bike exhaust

Stock exhausts from the factory are so well-engineered today that the goal of an aftermarket 4 stroke dirt bike exhausts is actually to refine and improve ride-ability vs. just trying to push peak horsepower numbers up on the dyno. Choosing the best exhaust for your 4 stroke will depend on your riding style, preferences, and budget.

With so many 4 stroke dirt bike exhausts on the market, it can be a tough choice choosing between them. Most riders will first want to gauge their max budget and then choose the exhaust which fits their specific riding style. In either case, the top 4 stroke dirt bike exhaust brands to consider are FMF, Akropovic, Pro Circuit, and Yoshimura.

Best 4 Stroke Dirt Bike Exhausts Reviewed

Putting the best 4 stroke exhaust systems to the test.

FMF is a hugely popular name in the dirt bike world. The brand is synonymous with high-quality, USA built-to-last durability. 

This slip-on exhaust is often paired with FMF’s Megabomb header to create a full exhaust system that comes close to rivaling FMF’s top of the line Factory 4.1 exhaust system. FMF didn’t cut corners on the materials list. Each muffler utilizes an aircraft grade aluminum sleeve for the canister and mount. High-strength stainless steel is used for the formed front and rear end caps as well as the mandrel bent mid-pipe. 

The FMF Powercore Exhaust ships with a 98dB low-volume insert but an optional 94dB quiet insert is also available separately. A removable USFS-approved spark arrestor is included. 

All the FMF pipes are manufactured in the US within their own plants and with the use of their own tooling. The best part of having exhaust systems built right at home is complete control over the quality of their products.

The FMF Powercore has been shown to increase mid-range and top-end power. This is the loudest 4 stroke dirt bike exhaust but can be remedied quickly as the optional quiet insert can be installed very easily. Overall, this is the best 4 stroke dirt bike exhaust for those on a budget but still looking for a great looking, durable pipe that provides a bit more mid-top end punch.

The FMF Factory 4.1 RCT is one of the best four stroke dirt bike exhausts for beginner riders or anyone interested in just smoothing out the power band of their engine and increasing ride-ability.

This exhaust can be purchased as a slip-on or full system which includes the FMF megabomb header. It utilizes only aerospace grade materials and is backed by the renowned FMF name so you know it is manufactured to meet very high standards and finish. The rear end cap is engineered for easy tuning to meet your own preferences by utilizing a retaining ring to keep standard or optional inserts in place. 

The FMF Factory 4.1 RCT retains the character of the stock power band but smooths out peaks and valleys resulting in a very usable power band that doesn’t feel excessively aggressive. This is accomplished while also reducing weight compared to the stock unit, moving that weight closer to the motor centralizing the mass improving handling and feel, and utilizing a shorter muffler that is less susceptible to crash damage which makes this a good aftermarket 4 stroke exhaust for enduro and extreme enduro. 

The FMF Factory 4.1 RCT is a great exhaust for those who want a great looking pipe that reduces weight and also provides a nice smooth powerband over stock. Go for the blue anodized titanium finish with carbon fiber end cap for the extra bling!

Akropovic is a house name in the performance aftermarket exhaust world. The Slovenian manufacturer boasts innovative, beautiful premium 4 stroke dirt bike exhausts as well as road-going equivalents. 

This exhaust by Akropovic is made entirely of titanium. Weighing in at only 9 pounds as a full exhaust system, it is guaranteed to please the handling and feel department after installing in place of the heavy stock exhaust system. The canister has a scratch resistant special coating which also makes for easier cleaning when the going gets dirty. The rear end cap is CNC machined from titanium to exacting tolerances and finish that Akropovic has become known for. 

The Akropovic Evolution exhaust smooths out the bottom end initial “hit” which can be a bit too harsh from the factory for many riders. This results in an easier to handle initial launch and power delivery in the lower rev ranges becomes much more manageable, particularly useful for trail riding which makes the Evo 4 one of the best exhaust options for woods riding and single track terrain.

The smooth bottom end makes a tangible difference in fatigue levels as the rider doesn’t have to wrestle the bike all day when powering out of the slow corners in lower gears. The power band is shifted upward with an increase in mid and top end of the rev range compared to stock which will be very welcome for most riders.

The Akropovic Evolution will favor riders looking for an increase in mid and top end power while also helping to smooth out low end grunt. The increased power is very manageable making this exhaust a great balanced option for many riders.

Pro Circuit is a renowned American company founded in the late 70’s by Mitch Payton while on the Southern California professional racing circuit. Thus “Pro Circuit”. Race-bred engineering and innovation guarantees satisfaction from even the most hardcore of racers. 

This 4 stroke dirt bike exhaust uses all titanium components including the header, mid-pipe, and canister shedding a ton of weight from the stock stainless steel affair. Machined brackets and joints guarantee long-lasting durability and TIG precision welding assures you this exhaust will endure many years of hard riding. Carbon fiber end cap adds that nice touch to an already brilliant finish.

The Pro Circuit Ti-6 exhaust aggressively shifts power towards the top end of the rev range. This lends itself well to riders who are going to keep their bike pinned and at optimum revs to take advantage of the character of this pipe.

Power is increased in the mid range as well but may feel hesitant down low compared to some other pipes. Once in the mid range though, this pipe will pull and pull all the way through to the next shift. It is a very quick 4 stroke dirt bike exhaust suited towards advanced or pro-level riders.

The Pro Circuit Ti-6 exhaust meets AMA noise restrictions and comes with a USFS spark arrestor as well. This is removable for easy switching between closed course riding and trail riding.

When it comes to proven exhausts, there is no doubt that Yoshimura has a racing pedigree second to none. 

Working in conjunction with Factory racing teams in both motocross and supercross, Yoshimura has built a brand on a foundation of winning championships and engineering that is always developed on the racetrack first.

The Yoshimura TRC utilizes some unique features: a pentagonal shaped muffler sleeve, poly resonant duplex chamber, and a 2 staged step baffle with carbon fiber cone end cap. All of this means that you get a hyper-lightweight pipe that looks great, makes generous power gains over stock, and also meets stringent noise and EPA requirements.

The Yoshimura TRC exhaust adds meat across the entire power band resulting in a very well balanced pipe which keeps ride-ability down low, fills in the mid range power impressively, and has an exciting top end punch. The power band is improved over stock so much that riders report being able to run a higher gear and still have plenty of punch out of corners without losing time. 

This is a “rider’s pipe” meaning feeling while riding is vastly improved and the benefits are actually usable when out there in the thick, not just inflated specs on paper and clever marketing slogans. This exhaust is so confidence inspiring it can actually make riding faster feel easier.

The TRC 4 stroke exhaust system can be utilized by riders of all skill-levels. The meaty power band allows beginners all the way to advanced riders to get the most out of the pipe thus the Yoshimura TRC wins for being the best four stroke exhaust for trail riding as well. Being the most powerful pipe out of the bunch combined with it’s impressive usability makes the TRC our top pick when it comes to after market 4 stroke dirt bike exhausts..

Increasing Horsepower

The real joy of fitting an FMF pipe to your bike is feeling the increased horsepower and torque when you’re out ripping. Your bike pulls noticeably harder than it ever did with the stock pipe fitted. Horsepower gains will obviously depend on the bike-specific application but you can rest assured no matter what bike you’re sporting that you will see power gains from fitting an FMF exhaust.

Understanding the concept of modifying your exhaust and the effects that has on your air to fuel ratio is the first step to fully answering this question. If you want the full picture, please read the section above titled: “Does Slip On Exhaust Damage Engine”.

If you want the short version: Yes, slip on exhaust adds horsepower BUT you must also modify your air to fuel ratio to accommodate the increased airflow of your new slip on exhaust. By updating your fuel map in your ECU or changing your jetting in your carburetor/s you will ensure you are not only maximizing horsepower gains from your slip on, but also that you have a smooth, usable power band.

Another quick way to bump up performance is to ensure frequent maintenance of your air filter ride with a good quality dirt bike air filter oil to prevent an dust and dirt from entering your fuel system. You also want to check your tires. There’s no point pushing the throttle on a smooth tire – pick up a set of the best rated dirt bike tires for maximum grip.

Most of us have experienced that dreaded dip in power in one specific part of the power band caused by having a slip on exhaust without the proper fuel mapping. Thinking of your slip on as a 2-part mod: fitting the exhaust properly and modifying your fuel map/jetting to match. 

Slip-On Exhausts & Engine Damage

The desire of those who fit a slip-on exhaust is to increase performance. It is contrary to that desire then to know that merely fitting a slip-on and going riding may actually decrease overall performance.
Anytime you introduce increased airflow on the intake or exhaust side of your engine you are tampering with the air to fuel mixture of combustion inside your engine.

If you increase airflow by fitting a slip on exhaust, you thus want to increase fuel to match. This can be achieved by installing a new fuel map to your ECU or simply changing jetting if you have a carbureted motor. Make sure to give your carb a thorough cleaning with high performance carb cleaner. Fitting a slip-on without changing fuel maps or jetting is not drastic enough of a change to cause immediate engine damage. If this

Over an extended amount of time, damage is possible but this is theoretical and depends on a number of variables. Be smart: if you add a slip-on exhaust then update your fuel map or jetting settings so you can actually enjoy the increased performance of the slip-on and you also benefit from the peace of mind that you are not at any risk whatsoever for engine damage over the longer term. Win-win!

2-Stroke Exhaust Compatibilty With a 4-Stroke Dirt Bike

It may seem convenient (read: lazy) to be able to grab that old 2-stroke pipe you’ve had laying around and throw it on your shiny new 4 stroke bike and see magical power gains and the deep exhaust note from the moto gods. Hey, that big expansion chamber looks trick on my new 4 stroke!!!

Without getting into exhaust gas dynamics, the fundamental basis of 2 stroke and 4 stroke engine principles is very different. If you just strap a 2 stroke exhaust onto your 4 stroke the bike will almost definitely run worse than just keeping the factory exhaust. Some riders have found no issues running the muffler only from a 2 stroke on their 4 stroke bike however.

The expansion chamber on a 2 stroke header is a different story however as it is specifically engineered for 2 stroke engines and unless you want to take a deep dive into wave dynamics and thermal volume principles then I suggest you leave this to the nerds, I mean engineers.

Related Performance Parts: Best Dirt Bike Pistons

FAQ’s – 4-Stroke Dirt Bike Exhausts

How Much Horsepower Does An FMF Pipe Add?

Average horsepower gain can be as much as 10.6 percent in certain areas of your rev-range! Peak numbers on the dyno increase an average of around 4 rear wheel horsepower and 3 lb/ft torque. The power curve after adding an FMF pipe mimics the stock curve showing an increase in power across the entire rev-range!

Does a Slip On Exhaust Damage A Bikes Engine?

Merely adding a slip-on exhaust to your bike does not in itself damage an engine. However, when fitting any modification to your engine you want to look at the bigger picture.

Can You Put A 2-Stroke Exhaust On A 4-Stroke Dirt Bike?

The fundamental basis of 2 stroke and 4 stroke engine principles is very different. If you strap a 2 stroke exhaust onto your 4 stroke the bike will almost definitely run worse than keeping the factory exhaust.

Last Checkpoint – Top Picks

Choosing the right 4 stroke dirt bike exhaust doesn’t need to be a difficult decision. Stick to the basics. Go with the leading brands and identify the price point you’re willing to pay. The top 4 stroke dirt bike exhaust brands include FMF, Akropovic, Pro Circuit, and Yoshimura. Each of these exhaust manufacturers offer great quality products that will meet your specific needs.

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