Parts FAQ

General Product Questions

It is completely normal for our headers to turn a bright red color when you first install and run your new FMF Racing header. This is a standard break in period that normally takes about 20 to 40 minutes. If the glowing persists after this break in period, it is recommended to check your jetting as it is possible your carburetor is too lean. If you are unable to properly jet your machine, contact a local certified technician to look at your carburetor.

FMF Racing does not ship anything overseas to retail customers. We do however have many distributors across the world, as well as online mail order companies that ship overseas. Check your local shops to see what distributors carry FMF Racing products in your country. Also with online mail order companies check which ones offer international freight.

FMF Racing does offer select items for replacement parts on your existing muffler. We offer end cap kits, decals, inserts and aluminum inlet sleeves. These items can be found by CLICKING HERE. We have a lot of customers calling into ask why we do not offer the outter shell or mounting bracket to our canisters. The reason for this is because all of our canisters and mounting brackets are hand-made together and cannot be sold as individual items. For 2-stroke we offer replacement end cap kits which can be found by CLICKING HERE.

I would first ask that question to the person/company that performed the motor work. They may have tested their motor combinations with a specific pipe, which would give you the same type of gains that they saw. 

For the most part though, all of our pipes will work with a modified motor. You will want to match the pipe with the powerband the motor was set up for. An FMF Rev pipe probably wouldn't be the best combination with a motor that was set up for tons of low end power.

There are a few differences between the shorty and standard length silencers depending on the model. Remember though, with 2-stroke tuning what you might consider a slight/small change has the potential of being a lot bigger than one might think. 

With the shorter length can and altered core size, we decrease the amount of backpressure in the muffler, which on a 2-stroke will increase throttle response and low to midrange power. Some models may see a slight decrease in over-rev though with the Shorty.

Many things. There are two criterias to look at, performance and features. Using a Powercore or Powercore 2 silencer will give your bike increased throttle response, a lighter and higher quality silencer with that factory look and sound.

The Shorty will give you even more throttle response and low end power. Because it's smaller you'll see even more weight savings and a louder sound level.

If you're really looking for that factory silencer, there's our Titanium 2 silencer. With the titanium stinger, front cap and cone end cap, you'll shave off tons of weight. Gains will be similar to our Shorty

Our Turbinecore and Turbinecore 2 are our Forestry Approved Spark Arrested silencers. These give you that factory look and power yet still being Forestry legal. This isn't something you'll have to take on and off, as all of our 2-stroke Spark Arrested silencers have the "Turbine-Dampening System' built into the core.

Also we have our "Q" silencer which takes our Turbinecore 2 to the next level of being sound friendly. This is our quietest silencer offered. This also has a Forestry Approved Spark Arrestor.

Last but not least to the 2-stroke line, the "Q-Stealth". The Q-Stealth is living proof FMF is the only exhaust company committed to bringing new technology to the 2-stroke enthusiast. Quiet on the trail as well as on the sound meter. No power loss. More packing volume-longer time between repacks. USFS approved spark arrestor. AMA and FIM enduro legal.

There are in some cases 20 or more possible pipe and silencer combos available from FMF for your bike.

Depending on what type of riding you are doing, we offer a wide variety of set ups. Check the in the "Search by Bike" to see what is available for your machine.

Our complete catalog is available online, as we are trying to be paper friendly and help save the enviroment, by going green not only with our exhausts! You can also use the "Search by Bike" engine to help narrow down what we offer for your machine.

If you have any questions that cannot be answered through our website, please call our dedicated staff members here at FMF Racing 310-631-4363 from 8am to 5pm Western time.

All of our testing during the R&D phase is around a complete FMF exhaust, pipe and silencer. We do check to make sure that the stock OEM silencer will fit up to our pipes. On a 2-stroke, the pipe has the biggest effect on what type of power the engine makes and when, the silencer is secondary to that. 

Read through the information we have available for both pipes and silencers to get a pretty detailed picture in your head on how each of our products are making power and how they all interrelate.

One word really, choice. We do it the same reason why Ford makes so many different types of cars and trucks. Someone looking for a smooth quiet ride probably wouldn't be happy in a 4X4 Turbo Diesel. 

Having that said, you can pick and choose the type of gains you're looking for and the features that best suit you, rather then us pre-determining them for you like other companies do. Check our search by bike engine at the top of your screen to help identify what we have available for your machine.

Depending on what model silencer you run with the stock pipe will determine how they work. All of our testing is done around one of our FMF pipes, but we do build them so that they will fit up to and work with a stock OEM pipe. Expect similar gains with our silencers on a stock pipe as you would when using it with an FMF pipe. In some cases the SST model pipes will only work with the SST model silencers. Check the fitment next to the SST pipes and silencers to make sure the fitment is correct.

Refer to our silencer information for specific features and power gains by product model.

Product Specific Questions

The newest addition to the line is the SST pipe. Think of the SST as a mix between the Fatty, and the Rev pipe with a little help from the rear SST section. This pipe gives an all around power increase similar to the Fatty, yet gives it even more mid and top like the Rev without sacrificing low end. This pipe offers a new power band that wasn’t available in the past, with its new technologies.

This year we've added titanium headers to the mix. We have something to suit everyone, from someone looking for a fair priced replacement all the way to that person looking for that factory titanium header. Here are your choices to choose from and why.


We offer our Hi-Flo and Powerbomb headers either in stainless steel or titanium. Our stainless steel headers offer you a lower priced header with increased durability compared to our titanium versions, because of the material and its lower costs and MIG and TIG welding. Don't let the lower price fool you into thinking they won't perform as well as the titanium versions though. These are modeled identical to the titanium headers and use the same CNC benders to insure proper fit every time. Our titanium headers are completely TIG welded and shave off pounds when compared to stock OEM steel headers. Since titanium is a higher grade metal, these headers are priced higher compared to our stainless steel versions. You don't get more exotic then titanium.

Hi-Flo vs. PowerBomb

Our Hi-Flo header is an upgrade to your stock header. We've taken the stocker header an improved it to the point that we're not drastically changing the powerband or losing power over stock. 

On some models, like the YZ400 we alter the routing so that it's tucked into the bike better so that it's less vulnerable to damage and so that you can change the oil filter without having to loosen or remove it.

Our Powerbomb header takes it to the next level.

The Powerbomb chamber has two functions. One it acts like a pre-muffler to knock down the sound level a bit and two increases power by increasing the rate in which the header can flow. When the exhaust enters the chamber, it expands and then cools which causes it to contract. This expansion and contraction actually speeds up the exhaust through the header. It also has a scavenging effect on the exhaust port, which will let a fresher air and fuel charge into the cylinder for a more efficient burn. This also creates even more power.

Don't be fooled by larger diameter headers increasing power everywhere. With a loss of backpressure at the exhaust port you will lose low end power in order to gain top end. Both the Hi-Flo and Powerbomb headers increase power throughout the entire power band.


The science behind the Megabomb header may be our greatest engineering accomplishment to date. You can bolt on a Megabomb with an existing FMF Racing slip on for as much as a 3hp boost, plus the Megabomb actually reduces noises levels by as much as 1.5dB. The MegaBomb header is revolved around our Supercross/Motocross riders and racers. The MegaBomb also works great in tight woods and technical single track trails, like most GNCC races. You will see the majority of your power increases on the low to mid range as well as broadening out the mid to top end over stock. This is the header that helped win the 2011 AMA Supercross, 2011 AMA Motocross, and 2011 Motocross of Nations Championships.

This works great for tight woods riding, supercross type tracks or for someone looking to boost that bottom end.

Keep this in mind. Having less backpressure (louder), the more top end power you’ll have. More backpressure (quieter), the more bottom end power you’ll have. This is true to a certain extent until you get out of the tuning range of the motor. A 250cc motor will only flow so much exhaust. If you’re looking for an all around power increase we recommend running 11-13 discs with the quietcore out. For more top end, add more discs and for more bottom end, run less discs with the quietcore installed. Don’t run less than 8 discs though.

Gold Series refers to the plated finish of our pipes. All our pipes other than the SST and ATV pipes are nickel-plated, which end up turning a slight gold color over time from the temperature, hence the name. The SST and ATV pipes have chrome plating for a higher luster.

Fatty pipes are designed to give the engine an all around power increase. We are not drastically altering the power band of the bike. This pipe will appeal to most people that are happy with the stock power band and just looking for more useable power everywhere.

Our Gnarly pipes have been developed and tested for the off-roader in mind. With thicker 18g steel construction, it will take the punishment you can throw at it. This pipe will shift and increase the power band so that it comes on sooner, pulls harder through the mid and smoothes out the high RPM surge. This was once called our Torque pipe, but it did not include the thicker steel construction.

The Rev pipe is designed for that rider that keeps it wide open. This pipe takes a little from the bottom and puts it up on top to keep it screaming. We offer this pipe for 80cc and 125cc's only and are recommended for higher skilled riders, as the power can be a little pipey. For outdoor high-speed tracks, this works awesome.

Riding and Racing

This is probably one of the most asked questions. The rumor mill has created several very creative meanings that we dare not share. For those of you wondering, FMF stands for ‘Flying Machine Factory’.

click here. We do not necessarily look for the fastest riders as much as we look for whom we feel would be the best representatives for FMF Racing.

FMF support vehicles are always on the move. We attend MX, SX, Freestyle, Desert, Enduro, GNCC and Cross-Country events across the USA all season long. 

For the latest schedule, click here.

Technical Support Questions

This is a common question we get here at FMF Racing. You cannot add a spark arrestor screen to any existing 2-stroke silencer. The reason for this is because all of our 2-Stroke silencers that have spark arrestors, are built into the actual core as a "Turbine Dampening System" that is welded to the core and is U.S. Forestry Approved. The three silencers we offer with spark arrestors are the Turbinecore's, Q Series and the Q-Stealth's.

For the majority of the time you will not need to use your existing stock OEM muffler clamp, unless stated in the directions for select models. We do recommend a light bead of high temp silicone with every application around the inner diameter of the mid pipe that slips over your header.

If your definition of power gains is, substantially increasing horsepower & torque, rate of acceleration, and the important fun factor, then yes you will gain lots.

Generally you’ll see a 5%-20% increase over stock depending on your application, but like jetting there are many variables to contend with. Don doesn’t put in countless hours of R&D time and lost sleep into a product to not have it perform like the way he feels it should.

We’ve been around long enough, that you can trust that any time you install an FMF exhaust product, you will definitely ‘ FEEL THE POWER ‘.

Our headers, whether it be the PowerBomb or the MegaBomb, are fitted to match an FMF series muffler. We do not recommend or guarantee you try to match it to a stock muffler.

For the most part, yes. We build our mufflers to be fully interchangeable between all of our products and stock components. This way you don't have to worry about something not fitting down the road.

There are a few instances where our muffler will only fit our header, but that's because we weren't able to get the gains/fit we wanted with out making it an FMF only version.

Some KTM’s slip-ons do not allow for an additional header to be added. We recommend you call one of our customer service representatives at 310-631-4363 before you make any purchases to verify the fitment on your machine.

As we all know sound is a major issue, which can effect whether or not we continue to enjoy our sport without offending others. Also your system performs best and will last longer when the silencer is properly maintained.

This depends on the type of riding and the amount of hours on the bike.

A two stroke running a little rich on the oil ratio will saturate the silencing media very quickly. On a big bore four frequent high speed riding will also shorten the life of the media. Also you should not allow water to enter the silencer outlet while washing your bike or ATV. Typically we would recommend every 15 to 20 hours on your machine to repack, but it differs for every level of rider.

Let your ears be the guide.

FMF sells replacement packing for all of our systems. With four strokes you want to use a high quality media with a High temperature rating.

There are a few things you can do to decrease the amount of sound your bike/ATV is putting out. Lets start with the exhaust, full race exhaust systems put out a lot of sound because they're smaller to save weight therefore they don't have a lot of packing material inside to help absorb the sound waves. If sound is a concern make sure you have the appropriate muffler installed on your machine. We offer many different exhausts that will address your needs.

Make sure your silencer/muffler has been re-packed lately and properly. Packing does go bad and will in turn make your machine louder over time.

Remember, not all the sound comes right out of the exhaust. If you've vented the air box or removed the lid, close it back up.

Also make sure all your nuts and bolts are tight so they don't rattle.

Also when a test is being performed, make sure you've got the transmission in neutral, with the clutch pulled in, this will also keep some of the noise down.

Depending on how big and where the dents are will determine how much power you’ll lose. The closer they are to the cylinder, the bigger it has an effect on how the pipe makes the power. Pipe measurements are pretty precise so even a small dent can change how the pipe works. Even carbon build-up over time will effect how it works. We aren’t setup to fix pipes here at FMF. 

Our main goal is to test, develop and produce exhaust products, and that’s what we do best here. There are many companies and dealers that can beat your pipe back into shape. Check in the back of any MX magazine for info.

We try and build all of our systems so that they require minimal jetting changes, if any. However some systems can benefit from jetting changes in fact with some two strokes it may be required to prevent engine damage. 

Click here to view our jetting guides. While we have many different models of jetting specs, your machine may not be listed. In this case we do recommend you consult with your local authorized techinician for jetting specs. 

Please keep in mind FMF's jetting specs are based on a stock motor with an FMF pipe. Other aftermarket motor parts may affect these specs; you would need to contact the manufacture in question for their jetting specs as necessary.

High performance silencers are made with performance and light weight as the prime objectives so one of the trade offs is having to maintain the silencing media or packing from time to time.