03/02/2026
Thinking of an engine upgrade for your Harley-Davidson?
Here at RG41 Ltd, we can carry out Stage 1–4 upgrades.
A Stage 1 upgrade is the most common upgrade, involving changes to the exhaust, air filter, and tuning to ensure the bike is running on the correct calibration. This can range from fitting an exhaust muffler through to a full exhaust system. We typically use a Harley-Davidson Screamin’ Eagle Stage 1 air cleaner, which does not change the aesthetics of the bike. We also offer three types of tuning: Diag4 tuning, Vance & Hines FP4, or our most commonly used system, the Dynojet Power Vision (PV), which can be used at a dyno centre.
A Stage 2 upgrade involves replacing the cam(s). This can instantly change the performance of the engine — whether you’re looking for strong low-end torque or higher RPM output, the choice is yours. We can source cams from Screamin’ Eagle, S&S, Fueling, and many more. We strongly recommend having the bike taken to a rolling road dyno to ensure correct mapping.
Stage 3 is the big jugs upgrade, increasing the engine capacity (CC). This upgrade can significantly increase both torque and horsepower, delivering strong and consistent power throughout the entire rev range. A running-in period is required, and a rolling road dyno is recommended, as new pistons and cylinders will have been fitted.
Stage 4 is all about power! This upgrade includes high-performance cam(s), big bore cylinders, and CNC-ported heads to produce the maximum power available. This is an expensive upgrade but will leave everyone else behind and more than a little jealous. The bike will need to be run in for several hundred miles, just like a brand-new engine. Caution — we do not take any responsibility if you cannot handle this level of power.
Dyno centre — rolling road tuning. The dyno centre we use has the ability to amend and refine Dynojet maps, smoothing out power delivery and improving overall performance. Once complete, you will receive a printout showing rear wheel horsepower and torque figures. Not carrying out dyno tuning can restrict performance and fuel economy. Why carry out engine work without properly dialling it in?
