What's Included in a Harley-Davidson Engine Conversion Kit? (And Is It Worth It?)
What Exactly Is an Engine Conversion Kit?
When Harley-Davidson riders talk about "conversion kits," they usually mean one of two things: a displacement conversion kit (like going from 883cc to 1200cc) or a crate engine (a complete, ready-to-install engine assembly). Both are available as genuine Screamin' Eagle products, and both serve very different purposes.
Here's what's actually in the box for each option we carry at New Castle Harley-Davidson.
The 883cc to 1200cc Conversion Kit
The Screamin' Eagle Sportster 883cc to 1200cc Conversion Kit is a bolt-on displacement upgrade for 883 Sportster models. It's not a full engine replacement — it upgrades the key internal components that determine displacement.
Typically included:
- Larger bore cylinders (matched to 1200cc spec)
- High-compression pistons
- Piston rings and gaskets
- Installation hardware
What it doesn't include: Your existing cases, heads, and bottom end remain in place. This is a targeted upgrade, not a full rebuild.
Result: More displacement, more torque, and a noticeably stronger throttle response — all from your existing Sportster platform.
Price: $2,149.95
Shop the 883cc to 1200cc Conversion Kit →
The 135ci Stage IV Performance Crate Engine
The Screamin' Eagle 135ci Stage IV Performance Crate Engine is a completely different category of product. This is a full, assembled engine — ready to drop into your bike.
What's included:
- Complete 135ci air/oil-cooled engine assembly
- Stage IV performance specification (high-flow heads, aggressive cam profile, optimized compression)
- All internal components pre-assembled and factory-tested
- Designed for direct installation into compatible H-D frames
What it doesn't include: External accessories like exhaust, air cleaner, or fuel management — those are typically sourced separately or retained from your existing bike.
Result: A ground-up performance engine with 135 cubic inches of displacement and Stage IV tuning. This is the choice for riders building a serious performance machine or replacing a worn engine with a major upgrade.
Price: $8,149.95
Shop the 135ci Stage IV Crate Engine →
Conversion Kit vs Crate Engine: Which Should You Choose?
- Choose the conversion kit if your engine is in good shape and you want a cost-effective displacement bump for your 883 Sportster.
- Choose the crate engine if you're building a performance machine from the ground up, replacing a high-mileage engine, or want the absolute maximum output available in a bolt-in package.
Installation: What to Expect
Both kits require mechanical expertise and proper tooling. We strongly recommend having either kit installed by a certified Harley-Davidson technician to ensure correct fitment, proper torque specs, and to protect your warranty. New Castle Harley-Davidson's service department is equipped to handle both installations.
Questions? Contact us or stop by the dealership — we'll help you figure out the right path for your build.