Harley-Davidson is arguably the most iconic motorcycle brand -- particularly in North America. Primarily a company that produces cruiser-style motorcycles, Harley-Davidson has focused on V-twin-powered bikes. One high-selling model, the 883 Sportster, has come in several different configurations throughout the years. Many owners are interested in modifications that will increase the power and performance of the 883 to approach the power level of bikes such as the 1200 Sportster. You can perform a number of modifications, depending on budget and skill level.
Remove any extra weight on the motorcycle using automotive tools. By lowering the weight of the motorcycle, you immediately increase the power-to-weight ratio -- even incrementally. Passenger grab handles, passenger foot pegs and other parts of the motorcycle not required for operation are prime targets for weight reduction.
Replace foot pegs and other parts with lightweight, performance alternatives. This type of modification may yield a small increase in performance, although these parts tend to be relatively pricey.
Replace the current air filter with a performance filter made specifically for the 883 Sportster. Companies such as K&N Performance Filters sell high-performance, high-flow air filters that give a slight increase in power.
Purchase and install a Powercommander module, which will allow you to modulate the fuel injection system with custom "maps." This tuning, which will allow for modest power upgrades and increased fuel economy, is only available for later models with fuel injection systems; you must modify models with carburettors in a different manner.
Install a carburettor jet kit, and have the carburettors tuned to allow for better air and fuel delivery to the engine -- and thus better performance.
Retune the suspension, and upgrade the braking system to achieve better handling performance. Have a professional perform this sort of work if you do not have the skills required.
Obtain a larger engine kit that will replace the 883 engine with the larger 1200 engine -- a far more difficult, expensive and involved modification that a professional should ideally undertake. In many cases, particularly if you own an older 883, you may find it more financially advantageous to purchase a different motorcycle with a higher-displacement engine.
Research to determine which performance gains you want to achieve and how much they will cost. Stay within your budget, and understand the limits to how much extra performance you can gain before it makes more sense to move to a motorcycle with a larger engine.
Secure the motorcycle safely with a motorcycle stand before performing any maintenance. Only perform modifications within your skill level and for which you have tools; leave any overly difficult or unfamiliar procedures to a motorcycle mechanic.