PROX Aluminium Rear Sprocket for YAMAHA YZ 125, YZ 250 1980-1998

The PROX aluminium rear sprocket is designed for YAMAHA YZ 125, YZ 250 from 1980 to 1998. 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.RA22080-48, 07.RA22080-49, 07.RA22080-51, 07.RA22080-52
• Available versions: 48 Teeth: ref. 07.RA22080-48; 49 Teeth: ref. 07.RA22080-49; 51 Teeth: ref. 07.RA22080-51; 52 Teeth: ref. 07.RA22080-52

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 : PBR · RFX
• Drive chain : RENTHAL · RENTHAL 520
• 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 125 1998
YAMAHA YZ 125 1997
YAMAHA YZ 125 1996
YAMAHA YZ 125 1995
YAMAHA YZ 125 1994
YAMAHA YZ 125 1993
YAMAHA YZ 125 1992
YAMAHA YZ 125 1991
YAMAHA YZ 125 1990
YAMAHA YZ 125 1989
YAMAHA YZ 125 1988
YAMAHA YZ 125 1987
YAMAHA YZ 125 1986
YAMAHA YZ 125 1985
YAMAHA YZ 125 1984
YAMAHA YZ 125 1983
YAMAHA YZ 125 1982
YAMAHA YZ 125 1981
YAMAHA YZ 125 1980
YAMAHA YZ 250 1998
YAMAHA YZ 250 1997
YAMAHA YZ 250 1996
YAMAHA YZ 250 1995
YAMAHA YZ 250 1994
YAMAHA YZ 250 1993
YAMAHA YZ 250 1992
YAMAHA YZ 250 1991
YAMAHA YZ 250 1990
YAMAHA YZ 250 1989
YAMAHA YZ 250 1988
YAMAHA YZ 250 1987
YAMAHA YZ 250 1986
YAMAHA YZ 250 1985
YAMAHA YZ 250 1984
YAMAHA YZ 250 1983
YAMAHA YZ 250 1982
YAMAHA YZ 250 1981
YAMAHA YZ 250 1980