Harley-Davidson Sportster 883 models produce 40 horsepower in stock factory condition. Several incremental modifications can be made to double the stock horsepower. Modifications should be grouped to maximize the horsepower increases at each stage of the process. Air-intake volume, exhaust capacity, electronic fuel injection or carburetor output, cam adjustments and electronic ignition modules are some of the more common performance-enhancing modifications available for the 883 engine.
883 cc to 1200 cc Conversion
Increasing the displacement of the engine will boost horsepower by about 10 horsepower over stock. Replacing the 883 cc heads, cylinders and pistons with 1200 cc engine components will convert the 883 engine to a 1200 using the same bottom end and transmission. The conversion is easily done, and kits are available with matched parts to eliminate the need for machine shop work and any complicated measuring or engine math.
Intake and Exhaust Circuit
Increasing the size of the air/fuel charge and capacity of the exhaust circuit increases the horsepower. Low-restriction intake and exhaust components open the circuit up and allow the engine to breathe better. The resulting increase in airflow boosts the volumetric efficiency and horsepower output of the engine. Low-restriction air cleaners and exhaust pipes coupled with bigger jets in the carburetor provide the increase in capacity for the system.
Ignition
Aftermarket ignition modules provide the engine with a pre-programmed or owner-programmable ignition-timing profile. Adjustments can be made with these modules to optimize the ignition-advance curve for performance applications and allow for adjustments for personal tastes or riding style. Ignition-system components, such as the spark plugs, spark plug wires and ignition coil, may be changed to high-output components to boost the ignition output.
Valve Train
Performance cams can change the timing and size of the engine's power band. A variety of cams are available with slightly different performance profiles to allow for personal preferences or needs of the particular vehicle. Valve and valve seat angles can be adjusted by a machine shop to further increase the flow through the intake/exhaust circuit. Intake and exhaust ports may be ported and polished to provide the lowest restriction to flow through the circuit. Cams are available in kits that include other necessary parts for the installation.
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