With so many upgrade options available for your dirt bike, you may find yourself wondering which you should consider first. Given the nature of dirt bike riding, most upgrades focus on weight saving or power increase like Dirt Bike Exhaust.
The ratio of your bikes maximum power, to the combined weight of you and your bike (power to weight ratio), is the most critical formula for increased performance. Simply put, the lighter you and your bike are, the easier it is for the engine to drive you forward.
There are other factors, of course. The right gearing, better tread, and aerodynamics all play a part, although, with dirt bikes, some of these factors are less critical.
At Motocross Advice, we are always looking for the best value for money options. For the average dirt bike rider, the single most effective, value for money upgrade you can make to your dirt bike is a new exhaust system. (We are not including the loss of a few KG body weight, which has to be the best value for money).
The combination of a lighter exhaust system, plus the extra horsepower generated makes your exhaust system upgrade a double threat to your mates or competitors on the track.
In this article, we will look at:
- Best exhaust systems for two-stroke dirt bikes
- Best exhaust systems for four-stroke dirt bikes
- We will also answer some frequently asked questions.
Here are our suggestions for the best exhaust systems for two-stroke and four-stroke dirt bikes.
Best Two-Stroke Dirt Bike Exhaust Systems
Choosing the correct exhaust system is critical for any two-stroke dirt bike. One of the visible features of a two-stroke exhaust is the oversize bulge in the downpipe. This bulge is actually an expansion chamber which helps the engine develop more power.
The expansion chamber works in the same way as a turbocharger, minus the complicated parts. As the piston moves on its downstroke, both intake and exhaust processes happen at the same time. As exhaust gases build up in the exhaust chamber, a vacuum is created which draws fuel and air into the cylinder. The resulting shock wave which is formed when exhausting gases hit the back of the chamber pushes any air and fuel which was drawn through to the pipe, back into the cylinder.
Two-stroke engines fell out of favour with some competitive motorsports a little while ago. Inefficiency and the environment were chief concerns. That trend seems to be reversing as more efficient designs are rolled out. If you are a two-stroke fan, then make sure you select the right upgrade for your bike. The correct pipe will give you increased power, and possibly a weight saving over the OEM parts.
1. FMF System Fatty Pipe with choice of Powercore 2 silencer
The fatty pipe has been a favourite of FMF fans for many years. One of the common attributes of two-stroke bikes is a lively, or snatchy throttle response. The power band can often be quite narrow, and when you hit it, your dirt bike may take off like a scalded cat!
The Fatty help smooth out the power curve and helps you access the power in a more controllable manner. This smoother power delivery is accessible across a much wider band too.
Being an heirloom product, the Fatty has 35 years of development behind it. It looks great too, with a nickel-plated carbon steel finish.
This system comes with a choice of end pipe (or silencer). Both are Powercore 2 range. You can pick from either the standard or shorty version.
The Standard Powercore 2 silencer features include:
- Lightweight extruded aluminium oval tube canister
- Quality stainless steel End cap and stinger
- High-performance perforated core
The Shorty Powercore 2 silencer additional features include:
Shortened canister length, which delivers improved low to mid-end performance. This option is an excellent choice for tight twisty tracks and supercross, where quick acceleration from low revs and sustained mid-range performance is critical.
- Not Street Legal
- Will require re-jetting
This Pro Circuit package offers a great deal of flexibility for a two-stroke dirt bike. You can choose from the works, Platinum, or platinum 2 downpipe, and match your choice to either the Pro Circuit R 304 Short, or 304 Factory standard silencer.
Your engine will be transformed with the platinum pipe. Smooth, accessible power is available across the entire rev range. The whole range is made from durable materials, and each has its own characteristics. Let’s look at those in more detail:
Pro Circuit Works Pipe
The Pro Circuit Works really helps smooth out the transition between mid-range and high revs. A lot of two-stroke engines will deliver an aggressive burst of power in the midrange, and then quickly fall off in the higher revs. This is particularly evident in 125cc and 250cc engines, where the power to weight ratio is critical. The Works pipe seems to increase the power output from the mid-range and on into the higher end in one smooth curve. This rider-friendly curve is no doubt the result of hours of factory testing, and the feedback from actual works riders and dyno tests.
Durability is enhanced with the use of CNC milled mounting plates which are less likely to suffer cracking or fracture. The Works pipe finish does require you to clean, dry and maintain after every ride. Leaving the pipe will cause surface rust, so if you are not a fan of post-ride cleaning and lubricating, you might want to skip to the Platinum.
Pro Circuit Platinum Pipe
The Platinum offers the exact same performance tweaks as the works. What sets it apart is the plated finish, which makes the pipe more resilient to wet and muddy conditions, and requires less rider maintenance.
KTM riders may require a flange kit if you choose the Platinum pipe.
Pro Circuit Platinum 2 pipe
Choose the Platinum 2 if you are riding more extreme off-road routes. The high gauge material used on the Platinum 2 is designed to withstand the increased knocks of rocks, tree branches and the like. The power delivery is broader on the Platinum 2, with more low-end delivery than the other models, making low-speed manoeuvrability a much easier task.
R 304 Shorty Silencer
The Shorty is for closed circuit racing only. If you are all about motocross and supercross, this is the silencer for you. The 304 Shorty excels at delivering maximum power while keeping the end of your bike lightweight and trim. There is much less chance of damaging your exhaust if you loop!
High-grade materials and an easy-access design mean a long life span and easy repacking of the silencer.
This is one of the most aggressive sounding “silencers” available. Expect to annoy the neighbours.
304 Factory Silencer
If noise is an issue, then look no further than the 304 Factory. This silencer has all of the performance mods of the R 304, with just a little extra weight and length. This is a sacrifice worth making if you are riding trails and public land.
- Given the range of options, not every combination is possible for every bike. Check for availability below
- Not Street Legal
- Re-jetting required
3. Bills Pipes Complete 2 Stroke Exhaust System
The Bills pipe system comprises of the MX2 pipe and silencer. Bill Cervera is a renowned engineer of over 35 years who has built factory pipes for some of the worlds leading teams and riders. He is a two-stroke specialist and is no doubt enjoying the resurge in popularity among the new generation of riders. His new range of pipes comes after a short hiatus from the industry.
Bills MX2 Pipes
The MX2 is handcrafted in the USA from 19 gauge carbon steel. They are incredibly good to look at, but as with all pipes, it is all about the performance gains. The MX2 does not disappoint here. With the MX2, most two-strokes experience an overall increase in useable power. The band runs from the mid-range, on into the top end. Some riders of 250cc engines report a drop in low-end grunt, although this is part of an overall smoother delivery of power.
The MX2 is undoubtedly ideal for anyone looking for a more trail orientated ride, with longer corners, and open sections where that higher-end power can be accessed easily. If you ride a 250cc on small closed circuits, with tight turns, you may need to adapt a little to the new low-end performance. 125cc riders experience less low-end power drop with the MX2.
- Not Street Legal
- Re-jetting may be required
- Requires oiling after every ride to protect the finish
4. Scalvini Full two-stroke Dirt bike Exhaust System
The Scalvini system is comprised of a cone section downpipe, and a choice of either steel carbon (Factory), or full carbon (Factory short) silencer. The Scalvini system appears to favour mid-top improvements in power for motocross and trails. Gnarlier or tight riding may be more challenging as the low end is not as useable as some of its competitors.
Scalvini Cone Pipe
The first thing that strikes you when looking at the Scalvini pipe is the coned section design. This is no surprise given the fact that they are Italian. The cone pipe is made up of several individually formed sections, which interlock neatly, and are hand-welded together. The result is a stunning factory look finish.
The Scalvini pipe delivers a focused power band increase at the upper mid, and into the highs. You will need to sacrifice some bottom end grunt for this more aggressive upper-mid and top-end performance. You will also need to have the skills to pay the bills. We feel that novice riders may not enjoy the benefits that more experienced riders will.
Despite the impressive power gains at the top and beautiful looks, many riders have had issues with installation. Expect a little more fettling when fitting.
Scalvini Factory Standard
The Factory Standard pipe is a lightweight aluminium can with a carbon end cap. It looks as swish as the downpipe and works adequately well as part of the system. The silencer can be repacked, and the combination works very well for most two-strokes.
Scalvini Factor Short (Full Carbon)
The Factory Short Carbon is a seriously-trick piece of kit. Italian design is renowned worldwide. Offering the same performance mods as the Standard silencer, this is the choice for circuit riders who are confident in taking their dirt bike up to the red line.
- Not Street Legal
- Re-jetting may be required
- Fiddly to fit, and may require some patience
- Suits aggressive and competent riders who can hit the high revs with confidence
- FMF Gnarly System With Turbinecore 2 Silencer
- For our last two-stroke recommendation, we are back to the FMF camp.
5. The Gnarly Pipe 2-Stroke MX Exhaust System
The Gnarly pipe benefits from the same 35-year pedigree as the Fatty. So far, our list has consisted of systems that suit trails and circuits. The Gnarly does what it says on the pipe. Explicitly designed to delivery punchy low-end power, the Gnarly will get you out the tricky stuff. The idea is to make your two-stroke behave more like a four-stroke at that critical bottom end. Ideal for tight and technical courses and complex woodland and forest trails.
The Gnarly is pressed from 18 gauge carbon steel and nickel-plated to withstand chips.
The Turbinecore 2 Spark Arrestor Silencer
If you are buying a downpipe that works exceptionally well on technical forest runs, then you will need to ensure you meet the strict limitations set by the forestry commission. The Turbinecore 2 is the ideal solution; designed to meet stringent noise level standards and with a spark arrestor fitted as standard.
This system is a turnkey solution for riders who want to tick all of the legal requirements for forestry riding in one package.
Overall performance is not the primary aim of this system; however, the Gnarly still smooths out the ride somewhat. Most two-stroke owners will notice that the carburation system breathes more easily.
- Re-jetting may be required
- 100% USFS Approved
- The Gnarly system suits technical trail riding, and slower tricker courses.
TOP 5 Dirt Bike Exhaust Systems for 4-stroke
How does a four-stroke system differ from a two-stroke? Well, the two-stroke chamber that causes the backpressure required for an efficiently tuned engine is the exact opposite of what is necessary for a four-stroke system.
In a four-stroke system, gases need to be expelled quickly, and via the most direct route possible. A four-stroke exhaust needs to be just the right diameter as if it is too large, exhaust gases will slow down too much. If the diameter is too small, then there is not enough room for gases to vent efficiently, which will also affect performance.
As with two-stroke exhausts, you will need to check to ensure you have ordered exactly the right combination for your bike.
1. FMF 4.1 RCT 4 Stroke Dirt Bike Exhaust System
We are kicking off with another industry favourite, the FMF 4.1 RCT system. Comprising of the RCT slip-on exhaust and a choice of two headers, the 4.1 RCT is the first choice for many teams in AMA Supercross Series, AMA Motocross Series, FIM Motocross of Nations and Monster Energy Cup.
The FMF RCT slip-on silencer combines technical know-how and high-grade materials to deliver a perfectly balanced four-stroke exhaust. A PAT pending core design balances sound restriction with intelligent pressure wave technology. This means a quieter than stock exhaust, with impressive power gains throughout the rev range.
Muffler material is moved closer to the motor to help centralise mass, and the quick snap end cap allows simple changes of the optional inserts. This rapid tuning system incorporates the necessary options for spark arresting and various sound levels.
The RCT offers significant weight loss over stock pipes. This is especially the case for dual pipe bikes, as the RCT converts to a single can system.
There is a choice of three finishes, and the system includes the mid-pipe.
The header pipe options for the RCT system include:
FMF Megabomb Header
FMF claim as much as 3HP can be gained over stock pipes through fitting the Megabomb. The internal design also gives up to 1.5DBs sound reduction. Another feature of the Megabomb is the increased low-end torque but without the extended length of a long header system.
The Megabomb will suit a rider looking to ride technical trails, and trickier circuits, as the low-end to mid-range grunt is ideal for these.
Available in titanium or stainless steel
FMF Powerbomb Header
As with its little brother, the Powerbomb is designed to drop the DBs over stock pipes. There are also some weight savings to be had too. The real benefit comes with increased bottom to top-end power delivery, making this combination the right choice for motocross, open trail, and supercross riders. Many riders report longer gears with the aftermarket system, allowing them to twist the throttle and get out of those corners without extra gear changes.
Stainless steel finish only.
- Not street legal
2. Yoshimura RS-4 Full System Motocross Exhaust
Japanese racing parts specialist Yoshimura is a well know brand in paddocks the world over. Their consistent performance and beautifully designed products capture the imagination. The RS-4 is a full system, with stainless header and mid-pipe.
The full system offers a considerable weight saving over OEM parts. The noise reduction is also immediately noticeable.
The silencer comes with carbon end cap and lightweight aluminium hanger brackets. Yoshimura also utilises a pentagonal shape box.
Very popular with 450cc riders, the power delivery of the RS-4 gives longer pull, and significant top-end gains.
Yoshimura offers an affordable, comprehensive refurb package. This service includes polishing and repacking, which removes a lot of the headache from maintenance.
- USFS Spark Arrestor with Enduro series
- Race series is not street legal
- Signature Series
- Remapping advised
3. Pro circuit Ti6/pro 4-Stroke Dirt Bike Exhaust System
The Pro Circuit Ti6 is a full titanium system, with carbon end cap. Specially designed for competitive circuit racing, this system ticks all of the compliance boxes for noise levels in the AMA and FIM series events.
The power band is a significant improvement over the previous Ti5 series.
Weight saving and durability are significantly increased over factory standard items. You will also notice an increase in top-end power delivery.
The standard Ti6 will not pass FIM or European noise regs; however, it does have the added advantage of a spark arrestor. This makes the Ti6 the correct choice for riders who need to bounce between circuit and trails.
- Requires retuning
- Make sure you select Pro for AMA/FIM compliancy
4. Big Gun Evo R Full 4-Stroke System
Not everyone is looking for race-focused performance. Sometimes you just want a reliable aftermarket product, that will trim some weight and deliver incredible all-round performance. The average dirt bike rider is looking for a system which can be used on trails, in forests and in the occasional circuit day too. With many riders unable to afford the luxury of multiple exhaust systems, the Big Gun Evo R is a fabulous all-rounder.
Constructed from high-grade aluminium and stainless steel, and arriving with a spark arrestor and race packing, the Evo is the most comprehensive package on the market.
The materials may be modest compared to other more exotic brands, but the power gains are significant. Torque and delivery of power are both vastly improved over stock systems. The low-end bark of the Evo is a fantastic sound too!
- Not legal for sale or use on emission controlled vehicles in California
- Not legal for road use
- Remapping advised
5. Akrapovic Evolution (titanium) 4-Stroke Dirt Bike Exhaust
If you own an older dirt bike, then you may want to check out the Akrapovic Evolution, Titanium system. Akrapovic has been an industry leader in aftermarket and performance sector for many years. Although this system is not available for many newer models, it would make an excellent upgrade for your older bike.
This system is for competitive riding and will deliver increased performance over ageing stock exhausts.
Weight reduction comes courtesy of an all-titanium construction. The kit includes comprehensive fitting components and spark arrestors, allowing you to configure the exhaust for your own individual requirement.
- Compliancy stops at FIM 2013
- Not road legal
- Always re-jet when fitting with a carburated bike
- Order exhaust gaskets when installing this product
There are systems to suit every requirement in our 2021 guide. Take the time to think about what your riding style and terrain demands of your bike.
Here are some more tips for you.
Frequently Asked Questions About Dirt Bike Exhaust Systems
There are a few questions which come up regularly when we talk to riders who are looking to upgrade their bikes exhaust system.
What is a spark Arrestor?
A spark arrestor is a metal gauze which is fitted inside your tailpipe to prevent sparks from exhausting. It is all too easy for sparks to start a wildfire in dry forest conditions, or brush. Most states require the use of a spark arrestor when you are riding in forests or places of increased fire risk.
How can I make my dirt bike exhaust quieter?
Exhaust noise can be a combination of many things. Rattling and vibration is often a contributory factor to increased exhaust noise. You should spend some time checking the mounting points and using a torque wrench to tighten all of the critical points.
If your exhaust has no baffle fitted, you may be able to buy a replacement for it by visiting the manufacturer’s website.
Also, packing should be checked and potentially replaced at regular intervals. If you have exceeded ten hours of ride time and not changed your packing, then you should do so.
If all of these tips make little difference, you may want to look at the replacement systems above, taking care to pick out those with decibel level limiters.
What are the legal decibel limits for dirt bikes?
The legal limits for decibels are subtly different, depending on where you reside, and what type of test is used. The most accurate way to ensure you are within the required limits is to check with your local state authority or track administrator.
How do you clean a dirt bike exhaust?
It is a good idea to clean and oil your exhaust after every ride. This is especially true of the exotic finished products, which are prone to rusting over if left wet.
If you clean your pipes after every ride, a serious restoration is unlikely to be needed.
- Wash off loose mud and dirt with warm soapy water. Rinse and dry.
- Clean heavily contaminated areas with Solvol Autosol and light gauge wire wool. Lightly marked patches can be cleaned with WD40/GT85 and Scotch Brite pads.
- Wipe over with a dry absorbent cloth to remove any residue
- Reseal the surface with WD40 or GT85 on a clean cloth
Spending a half-hour or so cleaning off and lubing your dirt bike after every ride is worth every minute. Investing this time into your ride will ensure your dirt bike parts last far longer, saving you money, and long days of hard restoration in the future!
We will be back with more Motocross Advice soon. Have fun out there!