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

On YAMAHA YZ 125, YZ 250 from 1980 to 1998, the PROX 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: PROX
• Manufacturer part numbers: 07.RS22080R-48, 07.RS22080R-49, 07.RS22080R-50, 07.RS22080R-51, 07.RS22080R-52
• Material: steel
• Available versions: 48 Teeth: ref. 07.RS22080R-48; 49 Teeth: ref. 07.RS22080R-49; 50 Teeth: ref. 07.RS22080R-50; 51 Teeth: ref. 07.RS22080R-51; 52 Teeth: ref. 07.RS22080R-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.

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?

ProX Racing Parts has been supplying engine and clutch parts to motocross riders since 1975, from its headquarters near Amsterdam. According to its catalogue, most of its parts are made in Japan, by manufacturers that also produce parts for the Japanese motorcycle makers.

Spare parts and items to plan

• Front sprocket : PBR · RFX
• Drive chain : RENTHAL · RENTHAL 520
• Chain lube : LIQUI MOLY 400 ml · MUC OFF

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