HOW TO RIDE LIKE A NINJA WITHOUT KILLING PERFORMANCE
“It is possible to escape death by perching on your enemy's eyelashes; it means you are so close that he cannot see you.” – Ninja Kawakami
Of all the issues surrounding off-roaders, noise has to be the biggest one. This article isn’t about whether noise hurts our beloved sport; we’re going to assume that’s been proven at this point. Most people who don’t ride don’t like the noise associated with our sport and it’s up to us to quiet ourselves down before they legislate us out of existence.
With that in mind, we’re going to review various methods of making your ride quieter without sacrificing lots of power, because let’s face it, how many of us can handle the power of these stock machines? Are we so good that we need not only the stock power delivery, but we actually need to increase it and bring along with it the associated decibels that come with that choice? For 90% of us the answer is a resounding no.
This article is primarily aimed at enduro/hare scrambles and woods/adventure riders, not hard core motocross racers. Racers in the top echelon and classes need every bit of horsepower they can wring out of their bikes at these closed-course competition venues. And many are governed by the AMA dB limits in order to race.
Now let's look at how to make your bike or quad so it's got some degree of stealth, allowing you to Ride Like a Ninja.
Stock vs. Aftermarket Exhaust Pipes and Silencers
In order to begin the process of quieting your ride, your bike must be running in the optimal state. Many times the stock pipe and silencer delivered with your bike provides the best reference point on where to begin in the quest to Ride Like a Ninja…
On most modern two-strokes, the pipe is a perfect piece of engineering, with lots of development time under its belt and is designed specifically to resonate at a certain frequency for optimal engine performance. We tend not to swap them out for aftermarket units until we’ve dented them up or the bike came delivered with some restrictive type of on/off road exhaust system.
When looking at the OEM silencers delivered with stock 2-strokes, they seem to be among the heaviest and ugliest components on the bike, so they come right off and get sold on eBay. We have kept the KTM silencer as it’s actually pretty a decent size and gives great power while being very stealthy and ninja-like.
When we do use aftermarket pipe and silencer setups, we’ve found the stock expansion with a FMF Racing PowerCore 2 silencer produces the best combination of sound and power for our Yamaha YZ144, and on our KTM 200EXC we find the FMF Gnarly pipe and stock silencer to deliver the perfect combination of torque and HP needed for tight woods and trails without being excessively loud.
One interesting side note in regards to aftermarket two-stroke expansion chambers and the sound they make…we have a FMF “Gnarly” pipe on one of our KTM’s and it seems really quiet. We think the thick 18 gauge construction of the Gnarly pipe keeps the noise down.
Four-strokes are a different story, with some variants being delivered with very restrictive exhausts systems straight off the showroom floor. In this case both head pipe and silencer replacement should be seriously considered. Some models actually are very loud and still quite restricted as delivered to the customer so the stock components need to be carefully examined when looking for the right combination of sound and power.
We’ve heard good things about the Pro Circuit Ti-4R components and we’ve used the FMF Megabomb header with the standard Q4 muffler on a CRF405R. FMF claims the header will “reduce noises levels by as much as 1.5dB, but we didn’t really notice any noise reduction until we mounted the Q4 on the back end.
So before you chuck that stock exhaust, carefully consider what component upgrades will deliver the best balance of noise vs. power, because what seems “fast to the ear” hardly is ever as fast on the dyno!
To help you decide what to keep and what to swap out, let’s look at some ways to keep quiet and Ride Like a Ninja…
Quiet Options: Silencers (2-Stokes) and Mufflers (4-Strokes)
For both 2 and 4-strokes, the noisy end of your exhaust is where dramatic impact can be made in noise reduction...is your silencer/muffler doing its job of actually silencing the bike or is it just passing hydrocarbons and more importantly, noise? Many aftermarket exhausts are available that are high flow due to their slightly longer length and internal exhaust gas routing configurations, dramatically reducing audible output.
One pioneer in this area is FMF Racing, who introduced their Q4 series to address just this issue. According to FMF: "The Q4 employs intricate chambers, baffles and proprietary multistage packing material” that makes it one of the least restrictive and quietest silencers available. Also available is the FMF TI Q4, which checks in at a whisper-quiet 92dB.
Other manufacturers that have seen fit to address this issue are Pro Circuit with their 296 series of off-road silencers and exhaust inserts, the SuperTrapp IDS2 which is tunable via multiple restrictor plates and the Big Gun Exhausts ECO Series and their Vortex Insert (available pre-installed).
In terms of silencers and mufflers, in our non-scientific seat of the pants testing, for our 2-strokes we found a stock expansion chamber with the FMF Q4 Stealth offered the biggest reductions in sound output without sacrificing gobs of power.
On most 4-strokes, using the stock head pipe with the FMF Q4 Hex muffler offered the best balance of power and sound without using an exhaust insert. This would exclude bikes with excessively restrictive head pipes.
Exhaust Insert Technologies
Exhaust inserts have their pro and cons but are certainly a cheaper alternative to ditching your expensive and lightweight muffler, and that makes sense for a lot of reasons.
The major player in this area is dB Dawg, which has been very successful in converting riders to their simple product. In fact the dB Dawg is so successful that some tracks encourage the use of the unit, which is especially effective on the larger bore four-strokes which are the loudest variety of bikes addressed in this article.
We took some time to speak with Clif Euler from DirtWerkz about the dB Dawg and its usage.
TT: Can you describe the dB Dawg installation process?
CE: The external models insert into the end cap of the silencer and tighten using two Allen screw type fasteners, this installation takes 5 minutes. The internal models require removing the end cap of the silencer and then inserting the dB DAWG.
The installation of the dB Dawg for the internal models are fairly easy and straight forward once the end cap is removed. Adding a tether is recommended for externally mounted units and can add a little extra time and effort to the installation.
TT: Is it removable and/or replaceable?
CE: The external models can be removed and reinstalled in just a few minutes, while the internal models require removing the end cap of the silencer. Once the end cap is removed, the internal model is easily removed and reinstalled in just a few minutes in most cases.
TT: Does it work with pipes that have a spark arrestor installed already?
CE: It depends upon the design. The requirement for the dB DAWG is that it needs a 2.5” straight of unobstructed clearance to support the insert.
TT: Have you noticed a loss in power when using the DBD?
CE: Personally on our family Honda CRF150 I noticed a drop on the bottom and also starting required a little more effort, but we easily fixed this by raising the needle clip one notch and that pulled it right back to pretty much where it was before.
TT: Do riders complain of loss of power when using the DBD?
CE: Generally speaking some of the 250’s or smaller bikes have reported some very minor loss on the bottom but with some minor carburetion, timing or injection tuning much of this can restored. Larger bikes don’t really seem to be impacted much at all. Most riders do not notice a difference, while some have reported a change in power delivery but not necessarily a loss.
Hyde Racing claims to have documented that when testing the dB Dawg on the dyno, “the power reduction is well below 0.5%, in some case only 0.15%”, and also notes that the unit “tends to make most machines run slightly richer, you will need to check your fuel mixture and jetting” after installation.
Other stand alone exhaust inserts available include the Pro Circuit Insert, the Vortex Insert, the Vance and Hines Quiet Insert (for XCR mufflers) and several varieties of the GYTR (Yamaha) Performance Quiet Muffler Insert.
What’s That Noise?
No silencer or muffler can keep the vibes mellow without being packed correctly. Many riders consider this a lost art, but we’ve done it many times and not only kept our rides at peak performance, but kept the noise down as well as increasing the longevity of our equipment.
We’re not embarrassed to say one particular Pro Circuit Short 2-stroke silencer in the shop has been rebuilt about 8 times, with just packing and rivets.
Here’s a quick overview of basic exhaust packing:
First, obtain an exhaust repacking kit. This should include the exhaust packing material and the rivets you’ll need to re-assemble the can. Make sure you have a pop-rivet gun for re-installation, and you’ll want to wear gloves to avoid the packing material from getting on your skin.
Take the can off the bike, remove the end cap from the body and drill out the rivets, being careful not to drill too deep into the core. Remove the core, the old packing material and clean the inside and core thoroughly. If you’re working with a generic piece of bulk packing, spend some time deciding the size and shape of piece(s) you’ll use. Do not over-pack.
Wrap the new packing material around the core piece and slide the finished assembly in the muffler to test the fit. To help this we use tie-wraps or tape to secure the packing.
In conclusion, there are a number of ways to quiet your ride and Ride Like a Ninja, and this article covers some simple ways to accomplish that goal. Staying as quiet as possible preserves your right to ride, so don’t lose it over a loud bike.