BRZ Viper 125cc Big Wheel Petrol Dirt Bike’s

BRZ Viper 125cc Big Wheel Petrol Dirt Bike

125CC YX 4-STROKE. 4-SPEED MANUAL. 17”/14” BIG WHEELS. UP TO 55MPH. 🏁⛽

The BRZ Viper 125cc Big Wheel is built for riders who have outgrown smaller pit bikes and want a much larger, more capable dirt bike.

At its heart is a 125cc YX 4-stroke racing engine, paired with an upgraded Mikuni carburettor and a 4-speed manual gearbox with clutch.

The big-wheel 17” front / 14” rear setup, inverted hydraulic front forks, upgraded rear suspension and hydraulic disc brakes give the Viper a substantially larger platform than the smaller BRZ models.

With a claimed top speed of approximately 55mph, an 88cm seat height and approximately 75kg maximum rider load, this is a serious junior/small-adult dirt bike designed for suitable off-road and private-land riding. 

⚡ Key Features

• 🔥 125cc YX 4-stroke racing engine
• 🏁 Upgraded Mikuni carburettor
• ⚙️ 4-speed manual gearbox
• 🕹️ Manual clutch
• 🚀 Claimed top speed up to approximately 55mph*
• 🔑 Electric & kick start
• 🎛️ Restrictable throttle
• 💥 Inverted hydraulic front forks
• 💥 Upgraded rear suspension
• 🛑 Hydraulic disc brakes front & rear
• 🛞 17” front / 14” rear big-wheel setup
• 🏗️ Steel rims
• 🪑 Gripper seat
• 🏁 Race-style exhaust
• 💡 Fully working LED headlight
• ⛽ 3.2L fuel tank
• 📏 Approx. 88cm seat height
• 📐 Approx. 122cm wheelbase
• ⚖️ Approx. 75kg maximum rider load
• 🎨 Blue & Neon Green options

🔥 125cc YX 4-Stroke Racing Engine

The Viper is powered by a 125cc single-cylinder YX 4-stroke engine.

It’s paired with an upgraded Mikuni carburettor, giving the engine a more performance-focused specification.

The 125cc engine puts the Viper firmly into the next class of dirt bike compared with the smaller 50cc, 70cc and 110cc machines.

⚙️ 4-Speed Manual Gearbox

The Viper uses a 4-speed manual transmission with clutch.

The gearbox follows the traditional:

N → 1 → 2 → 3 → 4

layout.

Unlike the BRZ 70cc and 110cc semi-automatic models, the Viper requires the rider to operate the manual clutch and gear lever.

That makes it much more suited to riders who already have experience with geared dirt bikes and are ready to move onto a larger machine.

🚀 Up To Approximately 55MPH*

The BRZ Viper has a top speed of approximately 55mph / 88km/h.

Actual speed will vary depending on rider weight, terrain, conditions, gearing, vehicle setup and other factors, so the quoted figure should be treated as a guide rather than a guaranteed speed. 

🎛️ Restrictable Throttle

The Viper is equipped with a restrictable throttle.

This allows the maximum throttle opening to be reduced when required, which can be useful when a rider is becoming familiar with the bike or progressing to a larger engine.

🔑 Electric & Kick Start

The Viper gives you both:

Electric start
Kick start

The combination gives the convenience of electric starting while retaining a traditional kick-start option.

💥 Inverted Hydraulic Front Forks

One of the standout upgrades on the Viper is its inverted hydraulic front suspension.

The inverted fork design is paired with upgraded rear suspension to give the bike a proper big-wheel dirt-bike setup.

The suspension is designed to handle suitable uneven off-road terrain while giving the Viper its larger-bike feel.

🛑 Hydraulic Disc Brakes

The Viper uses hydraulic disc brakes front and rear.

Hydraulic braking at both ends provides dedicated braking control for a bike of this size and performance.

As with all mechanical vehicles, the brakes should be checked before riding and maintained regularly.

🛞 17”/14” Big Wheel Setup

This is one of the biggest differences between the Viper and the smaller BRZ pit bikes.

The Viper runs:

Front: 17”

Rear: 14”

The larger wheel configuration gives the bike a much bigger overall stance and makes it particularly suited to taller riders who have outgrown smaller 14”/12” and 12”/10” machines.

The chunky off-road tyres and steel rims complete the big-wheel setup. 

🏁 Race-Style Design

The Viper has been designed with a proper race-inspired dirt-bike appearance.

It features:

• Race-style graphics
• Gripper seat
• Race-style exhaust
• Chunky off-road tyres
• Big-wheel configuration
• Inverted front forks
• LED headlight

It’s a substantial step away from the smaller children’s pit-bike format.

💡 Working LED Headlight

The Viper comes fitted with a fully working LED headlight.

This provides useful illumination for suitable private-land riding in lower-light conditions.

The bike should only be ridden where permitted and appropriate lighting and protective equipment should always be used.

📏 88CM Seat Height

The Viper has an approximate 88cm seat height, making rider height particularly important when choosing this model.

Key dimensions include:

Seat height: 88cm
Wheelbase: 122cm
Fuel tank: 3.2L
Maximum rider load: approximately 75kg

The larger dimensions make this bike much better suited to taller juniors and smaller adults than the compact BRZ models. 

👤 Is The BRZ Viper 125cc Right For You?

The Viper is towards the larger end of the BRZ junior dirt-bike range and is designed for riders who have already gained experience on smaller machines.

Want something smaller?

The BRZ 70cc Automatic is a much smaller fully automatic option.

Want to learn gears without a manual clutch?

The BRZ Semi-Automatic 110cc allows the rider to change gears without operating a manual clutch.

Ready for a full manual?

That’s where the BRZ Viper 125cc Big Wheel comes in.

It combines a 125cc engine, 4-speed manual gearbox and large 17”/14” wheel setup.

Want even more engine capacity?

The BRZ Viper 140cc Big Wheel moves up again in engine capacity, while the BRZ Race Pro 160cc Big Wheel and larger adult bikes offer further steps up.

If you’re unsure which bike is right for you, contact CMW Bikes before ordering and we’ll help you choose based on rider height, weight, experience and intended use.

📦 What’s Included?

• BRZ Viper 125cc Big Wheel Dirt Bike
• 3.2L fuel tank
• Electric start system
• Kick-start system
• Mikuni carburettor upgrade
• Inverted hydraulic front forks
• Rear suspension
• Hydraulic front & rear disc brakes
• LED headlight
• User/assembly documentation
• Assembly tools where supplied

Assembly Options

Boxed: Self assembly required

Fully assembled: +£99

The current CMW listing offers the fully assembled option for +£99. 

⚠️ Important Information – Off-Road Use

All vehicles supplied by CMW Bikes are intended for off-road/private-land use only unless specifically stated otherwise.

These are mechanical petrol vehicles and require routine maintenance, inspection and correct setup.

Please ensure:

• Brakes, chain, tyres, bolts and controls are checked regularly
• Appropriate protective equipment is worn
• The rider is suitably experienced for a manual 125cc dirt bike
• The vehicle is used responsibly and lawfully
• Permission is obtained from the landowner before riding on private land
• The bike is checked before every ride

🛠️ Warranty Information

Petrol vehicles include a 30-day replacement parts warranty.

The warranty covers manufacturing faults only and does not cover normal wear and tear, misuse, accident damage or maintenance-related issues.

Warranty exclusions include:

• Chains, belts and split links
• Tyres, tubes and wheels
• Brake components
• Clutches and pull starts
• Fairings and bodywork
• Spark plugs and similar service items
• Other parts subject to normal wear and tear

Customers may be required to provide photographs/videos of faults and fit replacement parts themselves where appropriate.

Technical guidance can be provided.

Nothing in these terms affects your statutory rights under UK consumer law.

View our full Terms & Conditions⁠

🚚 Shipping & Collection

Multiple shipping options are displayed at checkout.

We always aim to dispatch orders as quickly as possible, although slight delays can occur during busy periods.

If you select fully assembled, this can add 1–2 business days during particularly busy periods.

Local delivery and collection options are available at checkout.

Some stock is held at our distribution centre and may need to be transferred to our Cardiff store before collection.

📞 Call 07745 557756 before ordering if you need to check local stock urgently.

🏁 CMW BIKES

At CMW Bikes, we’re Cardiff’s local off-road dealer specialising in petrol and electric bikes, quads and scooters.

We stock a wide range of machines from BRZ, KLF, Dazzle, Stomp, Kayo, Revvi, VIPCOO and more, with options for younger riders, juniors and adults.

Whether you’re progressing from an automatic dirt bike or looking for a proper big-wheel 125cc manual, we’re here to help you find the right machine.

CMW Bikes – Cardiff’s local off-road dealer.