MOTO-MASTER Ultralight Steel Rear Sprocket for YAMAHA YZ 65 2018-2026

On YAMAHA YZ 65 from 2018 to 2026, the MOTO-MASTER steel rear sprocket fits in place of the original part. Bolted to the rear wheel, the sprocket takes all of the engine's force through the chain. Steel is the choice for durability: a steel sprocket sees off several chains where an aluminium one wears out, for a little more weight.

Specifications

• Brand: MOTO-MASTER
• Manufacturer part numbers: 620331144, 620331145, 620331146, 620331147, 620331148, 620331149
• Chain pitch: 420
• Material: steel
• Available versions: 44 Teeth: ref. 620331144; 45 Teeth: ref. 620331145; 46 Teeth: ref. 620331146; 47 Teeth: ref. 620331147; 48 Teeth: ref. 620331148; 49 Teeth: ref. 620331149
• Weight: 500 g
• Engine: 2-stroke

Choosing the right number of teeth

For the same bike, go for the number of teeth of your current sprocket (it's often stamped on it). More teeth on the rear sprocket shortens the gearing: more acceleration, lower top speed. Fewer teeth lengthens it. Even one or two teeth make a clear difference; if you change a lot, the chain length may need adjusting.

When to replace it?

• Teeth worn to a point or into a hook shape, worn down on one side only.
• Chain that lifts away from the sprocket when you pull it rearwards.
• Drivetrain noise, jerkiness or a chain that jumps under load.

Check the sprocket every time you service the chain. Always replace the rear sprocket, front sprocket and chain together: a new part running with worn ones wears out very quickly.

Fitting tips

1. Clean the hub and check that it isn't cracked or distorted.
2. Fit the sprocket the right way round (markings facing out) and tighten the bolts in a criss-cross pattern to the manufacturer's torque, with medium-strength threadlocker if the manual calls for it.
3. While you're at it, replace the front sprocket and the chain if they're worn.
4. Set the chain tension as per the manual, with the wheel aligned, then lube it with a suitable chain lube.
5. Recheck the bolt tightness and the chain tension after the first ride.

Why MOTO-MASTER?

Moto-Master is a Dutch brand founded in 1997 by Gaston Vernon that specialises in braking: discs, sintered pads and oversize kits. Its discs are designed in CAD and then laser-cut on CNC machines, with manufacturing in the Netherlands and ISO 9001:2015 certification.

Spare parts and items to plan

• Front sprocket : RENTHAL 506--420-14GP · RENTHAL 506--420-14P
• Drive chain : see the selection
• Chain lube : LIQUI MOLY 400 ml · MUC OFF 400 ml

Frequently asked questions

Aluminium or steel?
Aluminium is lighter and works well for motocross and racing. Steel lasts longer: it's the best choice for enduro, sandy terrain or if you put in a lot of hours.

Should the chain be replaced at the same time?
Yes, if it's worn: a stretched chain wears out a new sprocket in a few hours.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
YAMAHA YZ 65 2026
YAMAHA YZ 65 2025
YAMAHA YZ 65 2024
YAMAHA YZ 65 2023
YAMAHA YZ 65 2022
YAMAHA YZ 65 2021
YAMAHA YZ 65 2020
YAMAHA YZ 65 2019
YAMAHA YZ 65 2018