Motorcycle Crankshaft Bearing

BMT Bearing can be model-matched or customized to meet the shaft diameter, outer diameter, width, internal clearance, speed, and load requirements of different motorcycle engines.

Our products maintain stable operation under high speed, cyclic shock, vibration, and high temperature conditions.

What Is the Function of a Motorcycle Crankshaft Bearing?

1. Supports Crankshaft Rotation

Motorcycle crankshaft bearings provide stable rotational support for the crankshaft, allowing it to operate normally within the crankcase.

2. Reduces Friction and Energy Loss

Reducing friction between the crankshaft and stationary components through rolling contact helps reduce heat generation and mechanical losses.

3. Maintains Crankshaft Coaxiality

Controlling the crankshaft's position and oscillation during high-speed operation reduces eccentricity, vibration, and abnormal wear.

4. Bears Engine Loads

Crankshaft bearings need to withstand complex loads generated by the combustion process, piston reciprocating motion, and crankshaft rotation.

5. Adapts to High-Speed Rotation Conditions

Motorcycle engines operate at high speeds, requiring bearings to balance rotational accuracy, internal clearance, lubrication, and durability.

Technical Parameters

Application Scenarios

1. Scooter/CVT Automatic Transmission

Characteristics: Engine operates in the mid-to-high RPM range; crankcase space is compact; transmission end bears belt tension.

Application Location: Left and right main crankshaft bearings and connecting rod large/small end needle roller bearings.

2. Motorcycles and Brick Bikes

Characteristics: Frequent starts, gear shifts, and loaded driving; crankshaft force direction changes frequently.

Application Location: Main support positions on both sides of the crankcase; requires strong impact resistance and high rigidity.

3. Off-road Bikes and Off-road Racing Motorcycles

Characteristics: Violent jumping, frequent full-throttle acceleration, high vibration and high dust environment.

Application Location: High-strength crankshaft assembly; requires motorcycle crankshaft bearings with higher RPM and impact resistance.

4. Twin-cylinder and Multi-cylinder Large-Displacement Motorcycles

Characteristics: High power output; long crankshaft; combined axial and radial stresses.

Application Location: High-precision, high-load main bearings and multi-link large-end needle roller bearing combination.

Usage and Installation Precautions

1. Do not force it in

Do not directly strike the inner and outer rings of the motorcycle crankshaft bearing with a hammer. Use crankcase heating or professional cryogenic/hydraulic pullers instead.

2. Maintain a clean environment and initial lubrication

Before assembly, clean the inside of the crankcase with a clean cleaning agent to remove dust and metal shavings. During installation, apply sufficient clean engine oil to the bearing balls and raceways.

3. Ensure crankshaft dynamic balance and coaxiality

After pressing in the crankshaft, use a dial indicator to check the runout of the journals on both sides of the crankshaft (controlled within 0.02 mm).

If the crankshaft itself is bent, it will cause the bearing to be subjected to eccentric alternating forces and quickly fail.

4. Pay attention to oil supply and regular oil changes

Crankshaft bearings rely on oil splash or pressure lubrication. Regularly change the oil to the original manufacturer's viscosity grade to avoid oil dilution or the presence of metal dust, which can cause bearing pitting and spalling.

Customization Process

1. Requirements Communication and Parameter Assessment: Please submit your operating requirements, load/speed requirements, installation space or existing samples, and sketches to BMT Bearing.

2. Rapid Technical Drawing Production: The engineering team will create 2D/3D technical design drawings based on specifications and perform load calculations, expected within 1-3 business days.

3. Prototyping and Testing Confirmation: After drawing confirmation, rapid prototyping will be arranged, providing samples for customer installation and performance testing. Sample fees are waived, but shipping costs are the customer's responsibility.

4. Small-Batch Trial Production and Mass Delivery: After sample approval, mass production will commence on 20 automated production lines, with all parts undergoing full inspection in strict accordance with ISO 9001 / IATF 16949 standards before leaving the factory.

FAQ

Q: Why is the internal clearance of a motorcycle crankshaft bearing important?

A: Internal clearance affects bearing operating temperature rise, rotational accuracy, lubrication, and load-bearing capacity.

Insufficient clearance can lead to increased operating temperature rise and friction, while excessive clearance can cause vibration, noise, and decreased rotational accuracy.

Q: What are the typical symptoms of crankshaft bearing damage or wear?

A: Common symptoms include:

● A dull knocking or sharp grinding sound from inside the engine;

● Weak acceleration and a significant decrease in power;

● Abnormal engine vibration; decreased oil pressure;

● Metallic debris in the oil.

Q: Can crankshaft bearings be repaired, or must they be replaced?

A: It depends on the extent of the damage. Minor journal scratches or wear can be repaired through polishing, chrome plating, or spraying.

However, if the crankshaft is severely deformed, such as with a bend exceeding 0.05mm, or severely damaged, it must be replaced.

Q: What quality standards do your products meet?

A: All BMT Bearing products strictly adhere to original equipment manufacturer (OEM) repair standards and ISO specifications. Our factory is dually certified to ISO 9001 and IATF 16949:2016.

Before leaving the factory, all products undergo 100% dimensional, hardness, and rotational accuracy testing to ensure reliable quality.