MC300 performance package

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Introducing the MotoCult MC300 (288cc) Engine Package

The MC300 was designed specifically as a direct replacement for the original Janus 250 engine. Installation is straightforward—remove your stock engine, install the MC300, connect the factory controls and wiring, and you’re ready to enjoy a completely transformed motorcycle without cutting, welding, or modifying the frame.

Over the last several years, I’ve spent hundreds of hours developing performance parts for the Janus 250 line. Every dyno session, every carburetor, every exhaust, and every mile ridden has taught me something about what these motorcycles really want.

The MC300 is the next step in that evolution.

Built around a true 288cc four-valve engine, the MotoCult MC300 has been carefully developed specifically for the Janus 250 models. My goal wasn’t simply to build a motorcycle with more horsepower—it was to create an engine package that feels like it belongs in the bike.

The first thing you’ll notice isn’t the extra horsepower.

It’s how much smoother the motorcycle feels.

The MC300 produces noticeably less vibration than the stock engine, making the bike feel more refined through the handlebars, foot pegs, and seat. Twist the throttle and you’ll immediately notice the broad, effortless torque and strong pull throughout the RPM range. Whether you’re pulling away from a stop, climbing hills, or cruising down a back road, the bike simply feels more relaxed and more capable.

After countless hours of dyno testing and real-world riding, we’ve settled on a combination that delivers 22 rear-wheel horsepower and 16.4 ft-lbs of torque while maintaining excellent rideability and reliability. The dyno graph shows more than just an impressive peak number—the MC300 makes substantially more power throughout the usable RPM range, giving the motorcycle a completely different character.

Just as important, the MC300 retains the simplicity that has made the CG engine platform so respected around the world. Routine maintenance is essentially identical to the stock engine. Valve adjustments are just as straightforward, service is simple, and the engine is designed to be ridden and enjoyed—not constantly worked on.

The standard MC300 package includes:

• MotoCult-spec 288cc MC300 engine
• 28mm Nibbi PWK carburetor
• MotoCult proprietary intake
• MotoCult Performance exhaust
• 43T or 45T Rear sprocket
• Upper engine mount brackets
• Break-in oil
• Break-in instructions 
• Valve adjustment instructions 

For riders looking for even more performance, we also offer custom packages with a 34mm carburetor. These combinations produce outstanding results but require much more precise tuning, so they’re recommended for riders looking for maximum performance.

The MC300 wasn’t built to turn the Janus into something different.

It was built to make it feel like the motorcycle it always had the potential to be.

Frequently Asked Questions

Q: Do you offer a core credit for my original engine?
A: Yes. MotoCult offers a core credit for your original 250 engine, including engines that have been upgraded with MotoCult performance parts. The value of the credit depends on factors such as mileage, overall condition, and the components included. In many cases, returning your original engine can help offset the cost of your MC300 package. Contact us for a personalized quote.

Q: What does MC stand for?
A: MC stands for MotoCult. The MC300 is MotoCult’s complete 288cc engine package developed specifically for the Janus 250 models.

Q: Is the MC300 really 300cc?
A: The MC300 is a true 288cc, four-valve engine.

Q: How much power does it make?
A: Our standard MC300 package produces approximately 22 rear-wheel horsepower and 16.4 ft-lbs of torque on our dyno.

Q: Is this a direct replacement for my stock engine?
A: Yes. The MC300 is designed specifically as a direct replacement for the original Janus 250 engine. Installation is straightforward, requiring no cutting, welding, or frame modifications.

Q: Will I need to modify my motorcycle?
A: No. The MC300 package is engineered specifically for the Janus Janus 250 models, allowing it to install as a clean, factory-style engine replacement.

Q: Does it work with the stock airbox?
A: Yes. The standard package uses a 28mm Nibbi PWK carburetor and MotoCult’s proprietary intake, allowing the engine to retain the factory airbox for excellent filtration, rideability, and reliability.

Q: Is the MC300 more difficult to maintain than the stock engine?
A: No. Routine maintenance is essentially the same as the original CG-based engine. Valve adjustments are simple, regular service is familiar, and the engine is designed to be easy to own for years to come.

Q: Will my OEM or MotoCult fishtail fit the MC300 exhaust?
A: Yes. Both the original Janus OEM fishtail and the MotoCult fishtail are fully compatible with the MC300 performance exhaust, so you can keep the classic Janus appearance while enjoying the added performance.

Q: Can I order the MC300 with a larger carburetor?
A: Yes. We offer custom MC300 packages with a 34mm carburetor for riders looking for maximum performance. Because these engines require more precise tuning, we recommend having MotoCult build and tune those packages.

Q: Why would I choose the MC300 instead of upgrading my stock engine?
A: The MC300 offers more than just additional horsepower. It provides a true 288cc four-valve engine that is smoother, more powerful, and more refined while retaining the simple maintenance and reliability that riders appreciate about the CG platform. It’s the most complete performance upgrade available for the Janus JS250.

Q: What is included with the MC300 package?
A: Every standard package includes the MotoCult-spec 288cc MC300 engine, 28mm Nibbi PWK carburetor, MotoCult proprietary intake, performance exhaust, rear sprocket, and break-in oil.