PROX Aluminium Rear Sprocket for YAMAHA YZ 80, YZ 85 1993-2026

The PROX aluminium rear sprocket is designed for YAMAHA YZ 80, YZ 85 from 1993 to 2026. The rear sprocket is the large sprocket bolted to the rear wheel hub: together with the front sprocket and the chain, it transmits the engine's power to the wheel. Made of aluminium, it weighs much less than a steel sprocket, which cuts unsprung weight and makes the bike feel livelier.

Specifications

• Brand: PROX
• Manufacturer part numbers: 07.RA21093-47, 07.RA21093-48, 07.RA21093-49, 07.RA21093-50, 07.RA21093-51, 07.RA21093-52
• Available versions: 47 Teeth: ref. 07.RA21093-47; 48 Teeth: ref. 07.RA21093-48; 49 Teeth: ref. 07.RA21093-49; 50 Teeth: ref. 07.RA21093-50; 51 Teeth: ref. 07.RA21093-51; 52 Teeth: ref. 07.RA21093-52

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. Aluminium wears faster than steel, especially in sand and mud.

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 PROX?

Founded in 1975 and based near Amsterdam, ProX specialises in engine and clutch wear parts for off-road bikes. The brand has most of its range made in Japan, by OEM suppliers, for quality on a par with the original parts.

Spare parts and items to plan

• Front sprocket : RENTHAL · RFX
• Drive chain : RENTHAL 428 · AFAM
• 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 80 2019
YAMAHA YZ 80 2018
YAMAHA YZ 80 2017
YAMAHA YZ 80 2010
YAMAHA YZ 80 2009
YAMAHA YZ 80 2008
YAMAHA YZ 80 2007
YAMAHA YZ 80 2006
YAMAHA YZ 80 2005
YAMAHA YZ 80 2004
YAMAHA YZ 80 2003
YAMAHA YZ 80 2002
YAMAHA YZ 80 2001
YAMAHA YZ 80 2000
YAMAHA YZ 80 1999
YAMAHA YZ 80 1998
YAMAHA YZ 80 1997
YAMAHA YZ 80 1996
YAMAHA YZ 80 1995
YAMAHA YZ 80 1994
YAMAHA YZ 80 1993
YAMAHA YZ 85 2026
YAMAHA YZ 85 2025
YAMAHA YZ 85 2024
YAMAHA YZ 85 2023
YAMAHA YZ 85 2022
YAMAHA YZ 85 2021
YAMAHA YZ 85 2020
YAMAHA YZ 85 2019
YAMAHA YZ 85 2018
YAMAHA YZ 85 2017
YAMAHA YZ 85 2016
YAMAHA YZ 85 2015
YAMAHA YZ 85 2014
YAMAHA YZ 85 2013
YAMAHA YZ 85 2012
YAMAHA YZ 85 2011
YAMAHA YZ 85 2010
YAMAHA YZ 85 2009
YAMAHA YZ 85 2008
YAMAHA YZ 85 2007
YAMAHA YZ 85 2006
YAMAHA YZ 85 2005
YAMAHA YZ 85 2004
YAMAHA YZ 85 2003
YAMAHA YZ 85 2002
YAMAHA YZ 85 2001
YAMAHA YZ 85 2000
YAMAHA YZ 85 1999
YAMAHA YZ 85 1998
YAMAHA YZ 85 1997
YAMAHA YZ 85 1996
YAMAHA YZ 85 1995