Exhaust

Exhausts for your motorcycle

The exhaust carries combustion gases away from the engine, controls back pressure and pressure waves in the system, and therefore determines power curve, weight and sound alike. The right exhaust is as much an engine component as a cosmetic choice.

A system typically consists of the manifold or headers, an optional mid pipe with catalytic converter, and a silencer or silencers at the rear. Change one part and you change the flow through the entire system.

The choice matters because the engine is calibrated for a specific back pressure. A system that is too open can run the mixture lean and cost you bottom-end torque, while one that is too restrictive chokes peak power.

This guide covers measurements and markings, the difference between a slip-on and a full system, material choices, signs of wear, and the questions we get most often when customers are replacing an exhaust.

At Parts Denmark you will find exhausts from Akrapovic, LeoVince, FMF, Pro Circuit, HGS, Moose Offroad, Vance & Hines, Cobra, Freedom Performance Exhaust, Bassani Xhaust, Paughco, Thorcat Exhaust, Miller Exhaust, MCJ and MCS.

Use Find your bike on Partsdenmark.com to filter by year and model so you only see parts that fit. We ship from a large stock and offer free shipping on orders over €200.

Measurements, markings and layout

The figures you need before ordering are the pipe diameter at the joint, the insertion depth, the mounting bracket spacing and — if the bike is going to be used on the road — the approval marking stamped into the silencer body or on a welded-on plate.

Measurements to check

Always measure on the bike rather than guessing from photos, especially if an aftermarket part is already fitted somewhere in the system.

• Pipe diameter at the joint, typically 38-45 mm on inline fours and 44.5 mm (1 3/4") or 50.8 mm (2") on V-twins
• Whether the silencer slips inside or over the pipe — the two are not interchangeable
• Distance between the mounting bracket and the frame or footpeg bracket
• Clearance for luggage, pannier rails and crash bars on touring and cruiser models
• Whether a Heat Shield is required, and whether it is included or bought separately

Markings and road legality

If the bike has to pass inspection and be ridden legally on public roads, the approval marking is non-negotiable. Race parts are marked for closed-course use and must not be used on the road.

• ECE Street Legal silencers carry an E-mark with an approval number stamped into the body
• Approved versions normally come with documentation that must be kept with the bike
• Race silencers without markings are for track and closed-course use only
• A Noise Damper or db killer may be a condition of the approval and must not be removed
• The catalytic converter and lambda sensor must be retained on Euro 4 and Euro 5 motorcycles

Choose an exhaust to suit your riding

Your riding style determines whether you need a simple slip-on, a full system or a peak-power race exhaust. The table below covers the four or five typical scenarios.

Riding style	Type	Advantages	Disadvantages	Brands in the range
Road and touring	ECE-approved slip-on	Legal, easy to fit, moderate weight saving	Modest power gain	Akrapovic, LeoVince, MCJ
Sport and track days	Full titanium system	Greatest weight saving and peak power	Requires mapping, most expensive	Akrapovic, LeoVince
Cruiser and V-twin	2-into-1 or twin Mufflers	Plenty of character in the sound, wide choice of designs	Often needs new mapping and air filter	Vance & Hines, Cobra, Freedom Performance Exhaust, Bassani Xhaust, Paughco
Motocross and enduro, 4-stroke	Header with Silencer or full system	Better midrange response, easy to service	Needs regular repacking and cleaning	FMF, Pro Circuit, HGS, Moose Offroad
Motocross and enduro, 2-stroke	Expansion chamber (Pipe) and Silencer	Large gain in the chosen rev range	Dented pipes change performance, short packing life	FMF, Pro Circuit, HGS

On road bikes a slip-on is the cheapest place to start. It changes the sound and the looks and saves weight, but leaves the headers alone, so the standard calibration holds in most cases.

If you want measurable power, you need to step up to a full system, where pipe lengths and diameters are designed as a whole. It costs considerably more and nearly always requires custom fuel mapping.

For Harley-Davidson and Indian, the engine generation is decisive. There are systems and Mufflers made for Thunderstroke, Powerplus and Scout engines, and they are not interchangeable even though the brackets look similar.

Materials and variants explained

The material determines weight, durability, price and how the part looks after a couple of seasons. The three most common are stainless steel, titanium, and aluminium with a steel core.

Stainless steel

Stainless steel is standard for most headers and mid pipes because it handles the heat, welds well and resists road salt reasonably. It is heavier than titanium but clearly more robust against stone chips and crashes.

You will find stainless pipes and silencers from Bassani Xhaust, Thorcat Exhaust and Miller Exhaust, among others. The finish can be polished, brushed or ceramic coated in black.

Titanium and carbon

Titanium weighs around 40 percent less than steel at the same strength and is typically used on race and top-of-the-range models. It turns blue from the heat, which is normal and not a sign of damage.

Carbon sleeves are used on the outside of the silencer body to save weight. They cannot take direct contact with hot pipes, so spacers and the Heat Shield must be fitted as specified.

Aluminium and chromed steel

Offroad silencers often have an aluminium body with a perforated steel core and fibreglass packing inside. It is light and easy to service, but the aluminium discolours and goes dull over time.

Chromed steel dominates the cruiser segment at Cobra, Paughco and Freedom Performance Exhaust. Chrome looks good but yellows at the cylinder head if the engine runs lean, and needs polishing to stay presentable.

Wear, service life and maintenance

An exhaust wears from the inside through heat, vibration and moisture, and from the outside through salt and stone chips. The three things that fail first are gaskets, packing material and the welds at the brackets.

Leaks and gaskets

Soot or black streaks at a joint mean the gasket is no longer sealing. A leaking manifold lets in false air, causes an unstable idle and can confuse the lambda sensor.

Always fit a new gasket at the flange once the exhaust has been off — copper and fibre gaskets are single-use items and take a permanent set the first time they are fitted.

Silencer packing

The fibreglass packing burns away over time and the sound gets harsher and louder while back pressure drops. On a 2-stroke motocrosser the packing typically needs replacing after 10-15 riding hours, on a 4-stroke racer rather less often.

For most offroad silencers from FMF, Pro Circuit and HGS there are repack kits and a new Insert or end cap available, so you can refurbish rather than buy new.

Cracks, rust and brackets

Check the welds at the mounts and where the pipe meets the silencer body. Cracks almost always start where the vibration is concentrated, and they spread quickly once they have started.

Rot happens from the inside of the mid pipe on bikes used for short trips, because the condensation never gets a chance to evaporate. Get the bike properly warm regularly, including in winter if you are using it.

Fitting, mapping and sound

Most slip-ons can be fitted in an hour with ordinary hand tools, while a full system means removing radiators, tank or footpegs depending on the model. Allow plenty of time and have new gaskets on the bench.

Fit all parts loosely first. Only tighten the clamps and flange nuts once the pipes sit without tension and the silencer points correctly — otherwise you pull the system out of line and risk cracks later.

Use copper grease on the flange threads and tighten the nuts evenly in a crosswise pattern to the manufacturer's torque, typically around 20-25 Nm on a single-cylinder engine. Re-torque after the first heat cycle, once everything has settled.

If you replace the headers or mid pipes, you change the air/fuel ratio. On a V-twin that almost always means new mapping or a tuner module, and on sport bikes a custom file on the dyno.

If you want less noise, there are Noise Damper and db killer inserts available for many models. They cost a little peak power, but they are often the difference between a bike you can ride to and from the track and one you have to trailer.

Frequently asked questions about exhausts

These are the questions our customers ask most often when choosing between a slip-on, a full system and race parts.

Does a slip-on add power?

A slip-on typically gives a small gain at the top end and a noticeable weight saving, but the big power difference lies in the headers. Treat it as a sound, weight and design upgrade.

Do I need new mapping?

For an approved slip-on on a standard engine it is normally not necessary. If you change the headers, remove the catalytic converter or fit an open air filter at the same time, the fuelling has to be adjusted, otherwise the engine runs lean and hot.

On older carburettor bikes that means new jets and an adjusted needle position rather than electronic mapping.

Is the exhaust road legal in Denmark?

Only if it is E-marked and fitted as specified, including any db killer and catalytic converter. We state clearly when an item is ECE Street Legal or Approved, and when it is strictly for track use.

Why has my new exhaust turned blue?

Discolouration at the cylinder head is normal on titanium and stainless steel and is caused by the heat. If the colour is strong and extends a long way down the pipe, however, it can indicate too lean a mixture or retarded ignition timing.

Can I use my old silencer on a new pipe?

Only if the diameter and the slip direction match. Many Slip-Ons are designed around the exact dimensions of the standard pipe, and a new mid pipe from a different manufacturer rarely fits without an adapter.

If you are in doubt, measure up and contact us — it is quicker than returning a part that is 3 mm too small.

If you only need to change the rear section, you will find the full range under slip-ons, and if you want to rebuild from the flange back, complete solutions are listed under full systems. Use Find your bike so you only see parts for your exact model and year.

We offer European price matching, so if you find the same item cheaper at a European dealer, we will match the price. All items on Partsdenmark.com are sold with 2-year right of complaint, and you get free shipping on orders over €200.