Throaty sound from a motorcycle exhaust when revved can be music to the ears for a rider or passerby.
It’s no secret that stock motorcycle exhausts in current crop of production machines are designed to offer both form (design) and function (meeting decibel legislation). As a result, most exhaust notes are muffled and motorcycles are relatively quieter these days.
Are slip-on exhausts good or bad for motorcycles? Slip-on exhausts are mostly a harmless way of upgrading the motorcycles for both aesthetic and functional perspectives without too many hassles. Properly designed branded slip-ons will not harm the engine and can be safely fitted.
As long as the slip-on exhaust conforms with the approved decibel levels, there is no reason to worry.
What Does A Slip On Exhaust Do?
Since commercial motorcycles were invented over a century ago, the primary purpose of the exhaust system fundamentally hasn’t really changed when it comes to do doing its job of reducing noise.
Typical to both two- and four-stroke motorcycle/scooter engines, the exhaust unit is a thin pipe from the header (engine exhaust port) mated to a muffler (noise suppressor) unit.
Depending on the type of 2-wheeler, they can be pretty straight forward or complicated in design and appearance. In scooters, the exhaust pipe is usually shorter and welded to the silencer box or muffler unit as a single unit.
The engineering of the muffler or baffle plates for two-stroke and four-stroke motorcycles are completely different and are not interchangeable.
While some riders may stick to OEM exhaust systems, there are riders who seek more than just acoustic pleasure from their respective motorcycles. To serve their upgrade needs, the OEMs and aftermarket vendors offer a diverse range of bolt-on or slip-on exhaust kits.
In motorcycles, due to the forward placement of the engine, it requires a longer header pipe as the muffler unit is placed towards the rear end of the machine.
In most modern motorcycles the silencer box or muffler unit is detachable unlike most scooters. There could be some styling influences of the exhaust design depending on the type of motorcycle — street bike, tourers, cruisers, sports, adventure, off-road and so on.
In the case of multi-cylinder motorcycles, the engineering aspects may add-on a few things like a collector box. Current legislation and BS VI unleaded blended fuel (petrol with ethanol) specifications mandate catalytic converters and O2 sensors for fuel injector models.
So, What Exactly Is A Slip-On Exhaust?
Slip-on exhaust are exactly what the name suggests – a slip-on or a can muffler replaces the full system muffler provided by OEM.
Slip-on muffler units present a practical way and opportunity for enthusiasts to upgrade their motorcycles from both aesthetic or functional perspective without too many hassles.
Designs offered can range from retro, vintage, classic, modern and futuristic. Some riders even consider the slip-ons as style statements for their motorcycle.
Round and oval mufflers have been considered as traditional replacements and hence popular with motorcycle restorers.
Then came hexagonal and trapezoidal shaped mufflers and these are the latest in signature style statements for motorcycles.
Availability of exotic materials along with advanced design and production technologies, the design of bolt on or slip-on mufflers for motorcycles has reached an all-new benchmark level.
Classic and vintage designs are also now available for restorers.
Whatever product is chosen, the bottom line is that it’s a practical solution that doesn’t involve complicated or unnecessary modifications to the motorcycle.
What Makes Slip-On Mufflers So Popular?
Several reasons.
For starters, slip-on exhaust allows the user to retain the manufacturer’s stock exhaust pipe during the muffler/silencer box upgrade.
Secondly, it allows a modular approach for the system to be installed when working on a budget over a period of time.
There’s a huge choice of slip-on or bolt-on curated products for most type of motorcycles with various configurations and price points.
Apart from looks and audible entertainment, there’s an added advantage of a modest power upgrade that comes with these conversions free of cost.
How To Add Slip-On Exhaust In A Motorcycle?
As with any modification, planning, research and setting a budget is important. You don’t want to over spend or invest in incorrect products.
Decide on your goals first. Are you in just for looks, aural enhancement or extra horsepower?
Slip-on kits are quite flexible and one can adopt modular approach if working on a tight budget. You can add-on kit without disturbing the original parts.
Just bolting on a slip-on muffler may be an easy job as in most cases it doesn’t replace stock components like catalytic converters or oxygen sensors of the existing system.
However, in full kit systems (header pipes with muffler units), some extra work may be required like relocation of mounting brackets, sensors etc.
Full kits are for those enthusiasts desiring to enhance power from the engine besides having a visceral audio track.
Practical and uncomplicated Retrofitting slip-on muffler can be a DIY job for some, while others may seek professional help if there’s a mismatch of mounting points or requires some of its mounting hardware to be revisited.
A well-designed slip-on not only looks good but on an average can actually increase the engine’s output by 5% while reducing the gross weight of the machine.
Motorcycles with undertail or complicated exhaust system designs will require more than just casual skills for removal and retrofitting.
What To Buy?
Assuming that this is what you want, opt for a specifically designed system for your motorcycle model by a branded or specialist exhaust manufacturer.
Kerker, Yoshimura, Akrapovic are among some world-class names in this business. These specialist companies build dedicated exhaust kits comprising everything you need from the motorcycle’s cylinder head to the rear of the bike.
Avoid Knock-offs
Avoid knock-offs or fake copies as they will cause more harm than good to your motorcycle.
In fact, your experience with cheap or non-standard products will be short-lived and eventually prove to be expensive.
Top brands invest and innovate in material applications, acoustic and fabrication technologies for popular motorcycle models.
Their products come with superior construction and will offer long service life.
Slip-ons can be had in various metals and price points ranging from basic to exotic.
Expect to pay premium prices for products that deliver top performance features.
High end manufacturers like Akrvpovic consider stainless steel slide-ons as traditional and very basic. By their standards one would consider products made out this material as pedestrian or entry-level.
Akrapovic has enhanced the benchmark of aftermarket bolt-on mufflers or full systems by stepping into exotic materials like carbon fibre, titanium and curated alloys
Pitfalls of Slip-On Mufflers, if any?
Fitting a full exhaust system kit will also need additional work done to synchronise the motorcycle engine with hardware changes.
Ensure you install the correct one for your motorcycle model.
The most important is the fuel management department that needs to work correctly with the newly installed kit.
Typically, for carburettor-fed motorcycles, the jet set-up may need to be looked into and in fuel injected machine the fuel controller. Air flow is also an important consideration.
In general, slip-ons do not replace critical components like CATs and O2 sensors.
While, a full exhaust system is typically more complex to install than the mufflers-only system, flip side is the reward of greater power gain and a more aesthetically pleasant exhaust system.
Be prepared to replace critical parts that may break while you are working on the conversion kit.
For example, delicate oxygen sensors can be removed with normal tools but sometimes they are stuck and get damaged.
You can’t bypass the O2 sensor as its feedback is need for the fuel injector to operate properly.
Decibel Management
Some aftermarket slip-on exhaust makers offer muffler kits with a removable baffle that’s referred to as a decibel (dB) killer. The advantage of having this is that the baffle tube can be removed or put back for varying sound levels.
The way the unit is designed ensures performance remains of the motorcycle engine is unaffected by its presence or absence.
Safety Precautions
Exhausts operate at very high temperatures and depending on the engine’s condition and state of tune, header pipes can get hot and even discolour.
Experts recommend to install double walled pipes. The advantage is that the outer pipe remains relative cooler than the hot inner pipe and doesn’t discolor so easily.
If your bike hauls two people, then do invest in pipes that come with heat shielding. Most OEM and some aftermarket slip-on muffler makers come with protective heat shields.
They act as an insulating layer between the hot pipe/slip-ons and protect the rider/pillion from scalding their feet.
What Does the Law say on Slip-on Exhausts?
Some modifications are allowed for slip-on mufflers and most are not.
Never consider a slip-on muffler system that’s outrageous or social nuisance or illegal considered by law enforcement authorities.
Try to stay with a product that conforms with the approved decibel levels.
Any motorcyclist whose machine exceeds mandated dB parameters could face heavy fines or even have the motorcycle confiscated by authorities.
Does Slip On Exhaust Add Horsepower?
Slip on exhaust do not add any significant horsepower to the motorcycle and nor does it affect the performance.
While few experts claim a well-designed slip-on, on an average, can increase the engine’s output by 5% while reducing the gross weight of the machine, there isn’t sufficient research or evidence to back this claim.
Conclusion
For motorcycle enthusiasts seeking aural pleasure, retrofitting bolt-on or slip-on mufflers or silencer units is a great way to upgrade.
Properly designed branded slip-ons will not harm the engine and can be safely fitted.
Whether cosmetic or performance, various combos are available in the market at various price points.
Even if you are on a budget but have lofty goals, you can fulfill your desires.