Harley Davidson Staged Upgrades (I, II, III, IV)

Harley Davidson uses the terminoligy of "Stages" when referring to upgrading your engine. Partly because you cant upgrade your top heads and rockers (Stage IV) before you upgrade your jugs (Stage III) and Camchest (Stage II) so to make it easier to explain what you want to upgrade. The parts uyou will need to perrform these upgrades is different depending on the model bike you have. Milwaukee Eight vs Big Twin for example. Below you can find a breakdown of what is being upgraded and images to help understand.

The Path to Performance: HD Stage Upgrades

Every rider has a different goal. Some want a better sound for the weekend cruise, while others want to pull the front wheel off the ground. We specialize in taking your Harley-Davidson from factory-standard to a custom-tuned machine.

Stage 1: The Foundation (Intake + Exhaust + Tuner)

The first step for any bike. From the factory, Harleys are "choked" by emissions and noise regulations. A Stage 1 upgrade allows your engine to breathe.

What’s Involved: High-flow air cleaner, performance exhaust (slip-ons or full system), and a fuel management tuner.
The Result: A 10% increase in power, cooler operating temperatures, and that deep, iconic Harley rumble.
M8 vs. Twin Cam: On the M8, Stage 1 is vital to smooth out the throttle response. On Twin Cams, it’s the best way to get rid of that "sewing machine" sound and let the 96", 103", or 110" motor bark.

Stage 2: The Character Change (Camshaft Upgrade)

This is where the bike gets its personality. By swapping the camshaft, we control when the valves open and how long they stay open.

What’s Involved: Performance camshaft, adjustable pushrods, and high-performance lifters.
The Choice: Choose a Torque Cam for instant passing power at low RPMs (ideal for heavy baggers) or a Power Cam for a rush of speed that pulls all the way to the redline.
The Result: 20–30% more horsepower and a "choppy" idle that sounds as good as it performs.

Stage 3: The Big Bore (Cylinders + Pistons)

If "there's no replacement for displacement" is your motto, Stage 3 is for you. We increase the engine size without replacing the entire motor.

What’s Involved: Larger diameter cylinders and high-compression forged pistons.
The Result: Massive torque across the entire RPM range. Your bike will feel significantly lighter because it takes so much less effort to get up to speed.
M8 vs. Twin Cam: We can take an M8 114 up to a 122, or a Twin Cam 103 up to a 110 "Stomper" that rivals CVO performance.

Stage 4: The Ultimate Build (Heads + Throttle Body)

This is the "no compromise" upgrade. We optimize the top end of the motor to move the maximum amount of air possible.

What’s Involved: CNC-ported cylinder heads, a larger throttle body, and high-flow injectors.
The Result: The highest level of performance available. This is for the rider who wants to lead the pack and never look back.
The Stats: Expect up to a 40–50% increase over stock power. This turns a touring bike into a true performance bagger.

Ready to Level Up?

Select your engine type below to see specific kits, dyno charts, and the best aftermarket parts for your ride.

[Shop M8 Upgrades]	[Shop Twin Cam Upgrades]