125cc engine crankcase

Types of 125cc Engine Crankcase

A 125cc engine crankcase is a part of a 125 cc engine's crankshaft. It is usually located at the engine's bottom. The crankcase holds the crankshaft and connects it to the cylinder. It has a seal that prevents air from escaping the engine. Some people also refer to the crankcase as a crankshaft case. It is a case that holds the crankshaft of an engine.

The 125 cc engine crankcase is used in different types of motorcycles. Here are some of the most common types:

• Two-stroke crankcases: In a two-stroke engine, the crankcase serves as the air pump. The crankcase fills the cylinder with fresh air. When the piston moves down during a power stroke, it creates a vacuum in the crankcase. The vacuum causes the valve in the piston top to open. Fresh air enters the crankcase, replacing the air from the previous cycle. When the piston moves up, the valve closes. The incoming air helps push the piston up, ensuring the cycle continues. The air also helps lubricate the crankshaft. The cycle of the piston up and down also helps seal the valve in the piston top. The piston rings scrape the unburnt fuel and air from the cylinder walls. They help ensure the fuel and air mix remains intact for combustion. The crankcase design makes two-stroke engines powerful and lightweight, which is why they are mostly used in chainsaws, lawnmowers, leaf blowers, and small motorcycles. However, these engines are less efficient and emit more carbon compared to four-stroke engines.
• Four-stroke crankcases: Four-stroke engines have crankcases similar to two-stroke engines. However, in four-stroke engines, the crankcase does not pump air. Instead, it acts as a reservoir for the engine oil. The oil in the crankcase lubricates the moving parts of the engine. The four-stroke crankcase uses a reed valve or no valve on the piston to control air transfer. The absence of valves makes four-stroke engines more complicated and heavy. However, these engines are more fuel-efficient and generate low emissions.
• Single-cylinder crankcases: As the name suggests, single-cylinder engines have one cylinder, a crankshaft, and a crankcase. The crankshaft and crankcase work together to convert the up-and-down motion from the piston into rotational motion. This design makes single-cylinder engines simple, lightweight, and cost-effective. The single-cylinder design is good for low power output. For that reason, single-cylinder engines are commonly found in entry-level motorcycles and dirt bikes.
• Multi-cylinder crankcases: Multi-cylinder engines have more than one cylinder. The crankshaft in multi-cylinder engines can have multiple crankshafts. Each crankshaft handles its own cylinder. Multi-cylinder crankcases are more complex and heavier than single-cylinder crankcases. Multi-cylinder engines generate more power and are suitable for high-performance applications. Multi-cylinder engines are often used in sports bikes, cruisers, and touring bikes.

Specifications and maintenance of 125cc engine crankcase

The following are the specifications of the 125cc engine crankcase:

• Crankcase Size

  The 125cc crankcase is larger than the 50cc crankcase. A larger crankcase has more room for the crankshaft to move up and down. This allows for a larger stroke length, which increases the engine's displacement and power output. The 125cc crankcase is also smaller than the 150cc crankcase. A smaller crankcase has less room for the crankshaft to move, limiting stroke length. This affects engine displacement and power.

• Crankshaft

  The crankshaft for a 125cc engine is longer than the crankshaft for a 50cc engine. The 125cc crankshaft is usually about 5 to 10 millimeters longer. This increase in length contributes to the engine's larger stroke length and displacement. The crankshaft for a 125cc engine is shorter than the crankshaft for a 150cc engine.

• Connecting Rod

  The connecting rod for a 125cc engine is typically about 5 to 10 millimeters longer than the connecting rod for a 50cc engine. The connecting rod length is usually around 70 to 90 millimeters. The connecting rod for a 125cc engine is shorter than the connecting rod for a 150cc engine.

• Piston and Piston Rings

  The piston for a 125cc engine has a diameter that is 0.5 to 1 millimeter larger than the piston used in a 50cc engine. The piston for the 125cc engine typically has a diameter of 39 to 41 millimeters. The piston is smaller than the piston used in a 150cc engine.

• Cylinder Head

  The cylinder head for a 125cc engine is similar to the heads used in 50cc engines. It has one or two valves that control the intake and exhaust gases. The cylinder head for the 125cc engine is different from the heads used in 150cc engines. The heads are designed differently to improve performance and efficiency.

• Maintenance

  To maintain a 125cc engine, it is important to regularly check the engine oil level and change the oil every 2,000 to 3,000 kilometers or after 100 hours of engine operation. While using the bike, make sure the air filter is clean and replace it every 10,000 kilometers or 3 years. Inspect and clean the spark plug every 5,000 kilometers. Follow the manufacturer's specifications when using fuel. Ensure the cooling system is in good condition and top up the coolant as required. Keep the engine and its surroundings clean and free from dirt and debris. Adhere to the manufacturer's recommended maintenance schedule. Take the bike to an authorized service center for major engine repairs and overhauls. Regularly inspect the engine's performance and address any issues immediately.

How to Choose 125cc Engine Crankcase

Choosing the right 125cc engine crankcase can be a daunting task, but with the following tips, it becomes easy.

• Understand the Purpose

  It is important to understand the purpose of the crankcase before choosing one. The crankcase is the foundation of the engine and as such, offers support for the engine's internal components. The crankcase also houses the crankshaft and prevents oil from leaking. So, choose a crankcase that performs these functions effectively.

• Consider the Material

  The 125cc engine crankcase is made from different materials. Each of the materials has its advantages and disadvantages. The most common material for the 125cc engine crankcase is aluminum. Aluminum crankcases are lightweight and offer good corrosion resistance. Cast iron crankcases are strong and durable, but they are heavy and prone to corrosion. Plastic or composite crankcases are lightweight and corrosion resistant, but they may not be as durable as aluminum or cast iron. Choose a material that meets the needs of the task at hand.

• Check the Size and Compatibility

  The size of the 125cc engine crankcase is very important when choosing one. This is because a crankcase that is too small or too large will not fit properly, causing damage to the engine. Before choosing a crankcase, make sure it is the right size and compatible with other engine components, such as the cylinder head, piston, and connecting rod.

• Consider the Design and Features

  The design and features of the 125cc engine crankcase can affect its performance and durability. For instance, some crankcases have an integrated oil sump that holds the engine oil, while others have a separate oil sump. Crankcases with integrated oil sump are more compact and lightweight, while those with separate oil sump are easier to clean and maintain. Also, some crankcases have cooling fins or passages that help dissipate heat, while others lack that. Choose a crankcase with the design and features that meet the needs of the specific engine and its application.

• Quality and Reliability

  It is important to consider the quality and reliability of the 125cc engine crankcase before choosing one. This is because, with a reliable and quality crankcase, users can be assured of consistent performance and durability. To choose a reliable and quality engine crankcase, look for reputable manufacturers and brands. Also, read reviews and feedback from other users to know the quality and reliability of the crankcase.

• Budget

  The cost of the 125cc engine crankcase is an important factor to consider before choosing one. Crankcases that are made from high-quality materials and have advanced features are more expensive than those that are made from low-quality materials and have fewer features. Choose a crankcase that fits into the budget, but do not compromise quality and reliability.

How to DIY and Replace 125cc Engine Crankcase

Replacing the crankcase is a complicated process that requires a good understanding of the engine's mechanics. Below is a guide on how to replace a 125cc engine crankcase.

Tools needed

• Socket set
• Torx screw set
• Crankcase splitter
• Crankcase assembly tool
• New crankcase (matching the engine model)
• New crankshaft bearings and seals
• Torque wrench
• Lubricant/oil

Crankcase replacement steps

• 1. Preparation: Before starting, ensure the work area is clean and organized. Gather all the necessary tools and new parts. Disconnect the spark plug wire to prevent accidental ignition.
• 2. Drain Fluids: Drain the engine oil and any other fluids from the engine to prevent spills and contamination.
• 3. Remove the Engine: Depending on the vehicle, the engine may need to be removed from the frame or mounting components.
• 4. Disassemble the Engine: Use the socket and Torx screw set to disassemble the engine carefully. Take note of the assembly order or use a camera to document disassembly.
• 5. Crankcase Splitter: A crankcase splitter may be needed to separate the two halves of the crankcase. Follow the manufacturer's instructions for use.
• 6. Replace Bearings and Seals: Replace the bearings and seals on the new crankcase. Ensure they are properly lubricated.
• 7. Reassemble: Using the crankcase assembly tool, reassemble the two halves of the new crankcase. Torque the screws or bolts to the manufacturer's specifications.
• 8. Reassemble the Engine: Reassemble the engine components in the reverse order of disassembly. Refer to the documentation or photos taken during disassembly for guidance.
• 9. Reinstall the Engine: Once the engine is reassembled, reinstall it into the frame or mounting components.
• 10. Fill with Fluids: Refill the engine with the appropriate type and amount of oil or fluids. Double-check for leaks or spills.
• 11. Reconnect: Reconnect any electrical, fuel, or other connections made during disassembly.
• 12. Final Checks: Perform a visual inspection and ensure everything is in place and connected. Check the engine's movement and listen for unusual sounds.
• 13. Start the Engine: Reconnect the spark plug wire and attempt to start the engine. Allow it to run for a few minutes and monitor for any abnormal behavior or leaks.

Q&A

Q1: How do users know if a crankcase is compatible with an engine?

A1: Users can read the crankcase and engine specifications to know if they are compatible. They should also consult the service manual to provide detailed information on the compatible crankcase for a given engine.

Q2: What is the most common material used to make crankcases?

A2: The most common material used to make crankcases is aluminum. This is because it is a lightweight material and has good corrosion resistance. Aluminum can also be easily cast into complex shapes, which is ideal for making crankcases.

Q3: Can a damaged crankcase be repaired?

A3: Yes, it is possible to repair a damaged crankcase. However, this is only recommended if the damage is minor. Repairs can be done through l welding or metal stitching. Nonetheless, users should consult a professional mechanic to assess the crankcase and advise on whether to repair or replace it.