top 10 mod's and the psychology of why we do it

Riders upgrade bikes for many reasons: more power, better handling, greater comfort, or style. The “top 10” list below mixes performance mods (exhaust, intake, tuning), suspension/braking improvements, and practical upgrades (seat, windscreen, guards). Each upgrade ranks by impact or popularity, with rough cost, dyno’d power changes, and tradeoffs. We cover both high-end aftermarket parts (e.g., Yoshimura, Akrapovič, Dynojet) and OEM/genuine options. For each mod, we note typical street-legal vs. race-only constraints. Practical notes (installation, legality, safety) are included. A separate section examines the psychology of customization. A decision flowchart helps buyers choose mods by riding style (track, canyon, touring, daily). A summary table at the end compares costs, horsepower gain, difficulty, and ideal rider priorities for each upgrade. Citations draw on manufacturer data, dyno-test reports, and rider culture studies to give a thorough, analytical treatment.

1. exhaust: let that bagger breathe

Nothing kills the Death Before Stock attitude faster than a big American V-twin sounding like it just rolled off the showroom floor. On a bagger, exhaust isn't just noise. It's part of the engine's breathing system, part of the powerband, part of heat management, and—whether anyone wants to admit it or not—a huge part of the bike's personality.

We're not just talking about throwing slip-ons on the back. For a real performance-oriented bagger build, you're looking at the entire exhaust system: headers, collector design, pipe diameter, mufflers, catalytic converter location, and how all of it works with your intake, cam, and tune.

2-into-1: the performance choice

If horsepower and torque are priorities, a properly designed 2-into-1 exhaust is a common choice on performance baggers. Both cylinders feed into a single collector. That collector uses exhaust pulse scavenging to help move spent gases out of the cylinders.

Translation: it's not just louder; it can help the motor work better. Systems from companies like Bassani, Sawicki Speed, D&D, S&S, and other performance-focused manufacturers are popular on built Milwaukee-Eight baggers. They're designed around power, not just changing the exhaust note.

Depending on the motorcycle, exhaust, intake, tune, and other engine modifications, a complete performance exhaust can contribute meaningful horsepower and torque gains. But don't fall for the internet bullshit where someone claims bolting on one pipe magically added 20 horsepower. Exhaust gains are highly combination-dependent. The bigger advantage comes when the exhaust matches the intake, cam, and tune.

true duals: the classic bagger setup

Then you've got true duals. One cylinder. One pipe. Each side of the bike gets its own exhaust path. They give a touring bike that classic balanced look and unmistakable V-twin sound. For riders building a traditional custom bagger, cruiser, or long-distance machine, that symmetry can be worth more than chasing the last few horsepower on a dyno sheet.

A good true-dual system can still perform well. But if maximum power is the only objective, a properly engineered 2-into-1 will often be the direction performance builders look first. And that's perfectly fine. Not every bagger needs to be a fucking race bike.

headers + mufflers: build it your way

There's also the middle ground: performance headers paired with the mufflers you actually want. This lets you choose the header for flow and performance while choosing mufflers based on sound, appearance, and how obnoxious you want to be when leaving the neighborhood at 6:00 in the morning.

This is where bagger exhaust setups get interesting. Two bikes with similar motors can have completely different personalities depending on the combination. Deep and mellow. Sharp and aggressive. Old-school thunder. Or the kind of nasty cammed-up Milwaukee-Eight that makes everyone at the gas station turn around before they even see the bike.

what does an exhaust actually do?

The goal isn't simply to make the hole behind your engine bigger. A good exhaust system manages exhaust velocity, scavenging, and backpressure characteristics across the RPM range. Bigger isn't automatically better. A poorly matched pipe can move the power somewhere you don't want it or actually hurt low- and midrange torque.

On a 700–900-pound bagger, torque where you actually ride matters. Nobody cares that your dyno graph gained three horsepower at an RPM you hit twice a year if the bike became lazy coming out of a canyon corner or passing a truck in sixth. That's why exhaust selection should match the way the motorcycle is ridden.

• Canyon/performance bagger: strong midrange and throttle response.

• Touring bike: broad usable torque, manageable sound, and comfort over hundreds of miles.

• Big-inch/cammed build: enough exhaust capacity to support the airflow the motor can produce.

• Show/custom bagger: performance still matters, but appearance and sound may carry more weight.

  
  

the part everyone forgets: the tune

Once you've significantly changed how the engine breathes, especially when combining a full exhaust with a high-flow intake, the ECU needs to know what's going on. Proper tuning adjusts fueling and ignition to suit the new airflow. This is where the combination starts working as a system instead of a pile of expensive parts.

If a cam or big-bore kit is coming later, think ahead before buying the exhaust. Buying a pipe for today's stock motor and replacing it again six months later because your new 128-inch build hates it is an expensive way to learn that lesson.

typical bagger exhaust cost

Expect roughly $700–$1,500+ for a quality full exhaust system, depending on manufacturer, finish, and configuration. Premium stainless systems and specialized performance pipes can climb beyond that, while headers paired with separate mufflers can push the complete package higher still. Then budget for tuning if the bike needs it.

It's not the cheapest modification you'll make. But intake, exhaust, and tuning form the foundation that almost every serious engine build eventually builds upon. Unlike plenty of modifications, you'll experience this one every single time you hit the starter. More character. Better breathing. Potentially stronger usable power. Finally, your bagger sounds like the motorcycle you thought you bought in the first place. Death Before Stock.

2. high-flow air intake or air filter

Aftermarket: K&N high-flow filter, BMC conical filter kit, DNA/K&N “drop-in” filters or pod filters (street-legal on some bikes), Rapid Bike intake kits; OEM: Many bikes offer a “race air intake” kit (enlarged snorkel, filter, and heat shield). The Akrapovič case combined an open intake (via ECU remap) and exhaust. K&N’s literature claims multi-HP gains: e.g., K&N’s Rhino SxS air intake gave an “estimated 3.18 hp gain (11%)” on a 700cc UTV. For motorcycles, expect smaller gains.

Power/Torque: In stock bikes, gain is usually modest. A well-cited analysis reports “most ‘drop-in’ gains are modest” only if the OEM airbox is a bottleneck will you see hp rise. In practice, an aftermarket filter alone might add ~1–3 hp (≤5%) in the top RPMs. For example, on many liter sportbikes, an open filter + slip-on might show ~+1–3 hp on a dyno peak. The benefit is more pronounced at sustained high RPM or after other mods; reducing inlet restriction can “improve repeatability” under full-throttle. Torque: Minor effect; often unmeasurable.

Benefits: Better airflow usually yields slightly sharper throttle response and small power bumps. Washable reusable filter element also reduces maintenance cost over time. No weight change to speak of. Downsides: On some bikes, a loose pod filter (no airbox) can lean out the mixture or draw hot engine heat if not packaged well. Often requires a dyno tune to adjust fuel. Gains without ECU tune are usually very small.

Installation: Very easy. Many filters are direct replacements (5–10 minutes). Pod filters or race intakes may need minor fabrication (holes, hose changes). Safety/Legality: Usually street-legal if the OEM snorkel or heat shield is retained. Open filter pods might suck in rain or debris if not properly shielded.

3. ecu tuning / fuel controller

Aftermarket: Dynojet Power Commander V or ECU Flash, Bazzaz Z-Fi, Rapid Bike Race, Healtech Power Module; OEM: Some manufacturers (e.g., BMW, Ducati) offer dealer flash/dyno tune services or accessory “performance maps.” For example, BMW’s HP4 and S1000R race kits include specific ECU maps.

Power/Torque: Maps engine output to mods. Alone, a Power Commander (piggyback fuel injection tuner) or ECU reflash can unlock ~3–8 hp by optimizing fuel/ignition timing and removing rev limiters. Official data is scarce, but dyno shops often report mid to high teens percent gains when combined with intake/exhaust changes. Notably, Akrapovič requires “ECU remapping” for optimal results—highlighting that tuning is essential once hardware is freer-breathing. With full exhaust + filter, a flash might add ~10% power to stock (e.g., 8–12 hp on a 100 hp bike). Throttle Response: Often very dramatically improved (smoother, no flat spots).

Benefits: Unlocks full potential of other mods and improves engine “smoothness.” Can eliminate fuel-cut at high RPM, calibrate for altitude, allow use of richer “race” fuel maps. If done on a dyno, it can precisely tailor the curve. Downsides: Requires careful tuning; a bad map can hurt reliability. Standalone controllers cost $300–$800; professional dyno remap can be similar or higher. Some bikes (Euro models) require aftermarket electronics to achieve a full “Stage 1” tune.

Installation: Moderate to hard. Plug-in modules can be installed by a competent home mechanic in ~1 hr (plugs between injectors and harness). Flashing the stock ECU may need dealer tools or a third-party tuner with ECU access. Tuning usually requires a dyno session (~2–4 hours on a Dynojet or similar). Legality: ECU flashes can break emissions compliance. Many tuners sell disclaimers that “for race use only.” Some states allow dealer flash under warranty programs.

4. suspension upgrade (springs & shock)

Aftermarket: Progressive Suspension fork spring kits and 444 or 412 shocks; Öhlins fork cartridges or shocks; Race-Tech emulators; OEM: Factory heavier springs (some BMWs and Harleys offer “Heavy Duty” OEM springs), or software-adjustable suspension (found on some sports bikes) as a “performance part.” For instance, Progressive fork springs cost “From $123.95” and their 444 shocks from “$860.95”.

Benefits: Dramatically better ride quality and handling. Stock forks/shocks are often too soft or oil-starved, leading to dive under braking, wallow, and poor cornering. Upgrading springs (matched to rider weight) and damping (Progressive’s FST shocks dynamically adapt) yields much improved stability and corner grip. Handling: This is often the single biggest performance improvement a rider feels. Power: No horsepower change. Weight: Minimal (springs shock are similar weight to OEM). Comfort: Increased compliance on bumps if tuned right. Downsides: Costly and fiddly to adjust. A full fork rebuild by a shop can cost $500+.

Installation: Hard for average owner. Fork springs installation requires disassembly of forks (drain oil, remove caps) and reassembly—a 1–3 hour job per side for an experienced tech. Rear shock swap is easier (few bolts to remove), ~30–60 min. On modern sportbikes, aftermarket cartridge kits (Öhlins RMU, RaceTech Gold Valve) may be available, but those need a pro install. Safety: Use proper service manuals for torque specs. Progressive and others provide model-specific fit kits.

5. high-performance tires

Michelin Pilot Power/Road, Pirelli Diablo Rosso, Bridgestone Battlax, Dunlop Sportmax—typically the sporty or sport-touring lines. OEM: Bikes come with stock tires (often compromise rubber); upgrade to the same model of tire in a stickier compound is common (e.g., BMW sells Michelin PowerPure for some R bikes).

Power/Torque: None. Tires do not affect engine output but dramatically affect usable acceleration (via traction) and cornering. Wide or sticky tires let you put down more of the available power without wheelspin.

Benefits: Handling & Safety. New tires with better grip allow higher lean angles and shorter braking distances. More confidence and consistency in cornering. Often the first real performance mod riders do. Also improves comfort (new tires absorb bumps better than worn ones). Cost: $200–$400 per tire. Install: 30–60 minutes by shop (or with tire irons). Tradeoffs: Stickier tires may wear faster; very soft (race) rubber can be cold- or heat-sensitive.

6. brake upgrade (lines and pads)

Aftermarket: Galfer or Goodridge braided stainless steel brake line kits, EBC or Ferodo sintered pads, Brembo street calipers; OEM: Many bikes offer factory performance options, e.g., Harley’s Reflex-linked Brembo kit, or OEM steel-braided line kits.

Power/Torque: None (brakes don’t add power).

Benefits: Braking/Control. Braided lines remove sponginess, giving a firmer lever feel and more predictable bite (especially under repeated hard use). Better pads improve initial bite and fade resistance. Upgraded calipers/rotors (e.g., switching to larger diameter or 4-pot calipers) can shorten stopping distances. Generally one of the most cost-effective mods for riding confidence. Cost: Lines ~$80–$300; pads ~$20–$100; calipers/rotors hundreds to 1000+.

Installation: Moderate. Lines bolt on easily (bleed system afterwards). Pad swap is easy (loosen caliper, replace pads). Caliper/rotor change requires tools and possibly adapter brackets for rotors—1–2 hours with proper tools. Safety: Always bleed brakes and test thoroughly. Use DOT-approved components.

7. gearing: sprocket/chain

Aftermarket: Renthal or JT sprockets (steel or aluminum) and X-ring chains; OEM: Kawasaki has OEM “track” sprocket sets (wider gearing), Honda has lighter aluminum chain. e.g., Renthal sprocket kits are around $100–$150.

Power/Torque: No change in engine output, but changes acceleration vs. top speed. Acceleration: Fewer front or more rear teeth multiplies torque to the wheel. A larger rear sprocket (+1 tooth) can yield noticeably quicker 0–60 times and lower cruise RPM (at the cost of ~5–10% lower top speed).

Benefits: Throttle Response/Feel. Quickens acceleration and makes midrange feel stronger, especially if bike is tall-geared for highway. Can be tuned for rider preference (higher gearing for freeway/high-speed stability, lower gearing for twisties). Also, replacing chain and sprockets is required maintenance—a fresh chain with good o-rings reduces friction and wear. Cost: Typically $70–$200 for a sprocket kit plus $50–$150 for chain. Install: Moderate—swap of sprockets and chain takes ~1–2 hours (chain press and alignment tools needed).

8. comfort upgrades: seat and handlebars

Seat: Sargent, Corbin, or custom foam modifications—often $300–$600. Handlebars/Controls: Adjustable levers (ASV, CRG), risers (Ergo-Riser, Rox), heated grips ($100+). Windscreen: taller or adjustable shield (Givi, Zero Gravity)—$150–$400.

Power/Torque: Zero.

Benefits: Comfort and Ergonomics. For touring or daily riding, reducing fatigue is huge. A better seat with more padding or a different shape greatly increases comfort on long rides. Handlebars or clip-ons with different geometry can alleviate back/neck strain. A windscreen cuts buffeting at speed, reducing fatigue. These mods don’t add speed, but more comfort means you can ride longer and focus better. Cost & Install: Varies—seat swap takes minutes (bolt-on), handlebar risers an hour, windscreen swap ~30 minutes.

Installation: Generally easy. Safety tip: ensure any new mirrors or electronics attached to bars (GPS mounts, grips, etc.) are secure and not interfering with steering.

9. lighting and electronics

LED headlights (Philips X-tremeUltinon, Denali): ~$100–$200; Auxiliary lights (Whelen or Nilight): $100–$300; Upgraded blinkers and tail (Smoked LED kit: $50–$150). OEM: LED upgrade kits from BMW, Ducati, etc.

Power/Torque: None.

Benefits: Visibility & Safety. Brighter headlights improve night riding. Running/turn lamps can make you more conspicuous to cars. Comfort benefit: some riders add USB charging ports or heated grips. Install: Moderate; swapping headlight bulb is usually plug-n-play, but ensure correct housing (beam pattern) to avoid blinding traffic. Always check DOT/ECE compliance for street use.

10. crash protection (frame sliders, bars, guards)

Examples/Links: Frame sliders: R&G, GB Racing, or OEM (Ducati Performance sliders), ~$100–$200. Engine guards: Hepco & Becker crash bars ($400+); Sliders: swingarm spool sliders (Vortex ~ $30/pair).

Power/Torque: None.

Benefits: Protection in a crash or drop. Sliders and bars help prevent damage to fairings, engine cases, and ergonomics if the bike tips or slides. They can save thousands by sacrificing a $50 slider instead of a $1000 crankcase cover. Some guards also protect radiators or footpegs. Cost: Usually hundreds (bars) or lower (sliders).

Installation: Varies. Frame sliders bolt to engine mounts (1–2 hr); crash bars attach to frame/crash mounts (2–3 hr, sometimes require removal of bodywork). Safety/Legality: Usually street-legal (they don’t affect bike’s compliance), but check that sliders don’t interfere with cornering or passenger pegs.

installation checklist & notes

For each upgrade, follow best practices:

• Torque Specs: Use a service manual. Tighten all fasteners to spec (especially suspension and engine mounts).

• Alignment: After wheels/suspension work, check alignment (chain/sprocket changes may need alignment adjustments).

• Bleeding: After brake line install, bleed thoroughly.

• Fuel and Tuning: After intake/exhaust/ECU changes, lean or rich conditions can appear. Dyno tuning or at least wideband AFR checking is recommended.

• Legal Compliance: Verify local laws. Many performance mods (open exhausts, engine remaps, air intake changes) are for track use only. Adjust usage or parts accordingly.

• Safety Gear: Wear gloves and safety glasses when working. Use a stand for wheels, and ensure the bike is stable on a lift or paddock stand.

  
  

the culture of modifications

Motorcycle customization isn't just about performance; it’s a form of personal and group identity. Riders often describe their machine as an extension of themselves. Ethnographic studies of biker subcultures note that motorcycles and their parts serve as symbolic consumption—buying into a “biker identity” through gear and rides. Mods signal values: a loud pipe and slick tail tidy shout “outlaw” or “track rat,” while a cushy seat and grips say “touring, all-day comfort.” Enthusiast forums and rallies reinforce norms. For example, 1960s Harley rally photos show hand-controls and whitewall tires as badges of belonging.

Psychologically, riders often cite freedom and expression as motivations. Upgrades can be about mastery and challenge. Tuning an engine is a technical skill and source of pride. The “Death Before Stock” motto popular in some circles epitomizes the idea that a bike is only worthwhile if it’s been personalized or pushed beyond stock specs. This reflects a reward/risk mindset: pushing a bike to the edge (both in power and style) brings exhilaration and status. At the same time, community and belonging are huge drivers. Riders swap tips on the best mods, compare dyno charts, and show off their builds at meetups. Social media and clubs reinforce the belief that a custom bike is more authentic.

In sum, modifications serve multiple psychological needs: thrill-seeking (adrenaline from more power or leaner angles), self-expression (“this bike is me”), and camaraderie (bonding over wrenching and racing). Ethnographers note that what might appear as mere consumption is actually how riders construct identity: the bike becomes a mobile billboard of personal story and subcultural values. People who shout “Fuck stock!” often do so in the spirit of “I’m passionate, not plastic.” The logic may sound rational (better parts = better bike), but it’s deeply emotional: mods can make riders feel braver, more confident, and more connected to the biker tribe.

buyer’s decision flowchart

Deciding which upgrades to buy starts with your goal as a rider: Are you chasing lap times, twisty-road fun, long-distance comfort, or daily reliability? The flowchart below offers one simple way to prioritize upgrades by rider focus.

This is just one approach; often bikes get a mix. But it’s wise to match upgrades to your priority: track riders want power and grip; canyon riders want nimble handling; tourers want comfort and wind protection; commuters want lights and reliability.

Each upgrade’s cost and power figures above are general. For example, adding a full exhaust plus ECU tune can raise peak power by ~10% on a 100 hp bike (i.e., +10 hp), whereas simple comfort mods (seat, grips) give no power but are invaluable to the touring rider. For handling mods like suspension and tires, the “gain” isn’t measured in HP but in better lap times or corner speed.

Sources: Manufacturer performance data and dyno charts; K&N and BMC testing; industry pricing; rider culture research.