PROX Front Sprocket for KTM SX 85 2003-2017

On KTM SX 85 from 2003 to 2017, the PROX front sprocket fits in place of the original part. Mounted on the gearbox output shaft (countershaft), the front sprocket passes the engine's torque on to the chain. Every tooth is loaded on every turn of the wheel: a worn front sprocket makes the chain jump and speeds up wear on the whole drivetrain.

Specifications

• Brand: PROX
• Manufacturer part numbers: 07.FS61004-12, 07.FS61004-13, 07.FS61004-14, 07.FS61004-15
• Available versions: 12 Teeth: ref. 07.FS61004-12; 13 Teeth: ref. 07.FS61004-13; 14 Teeth: ref. 07.FS61004-14; 15 Teeth: ref. 07.FS61004-15

Choosing the right number of teeth

Start from the stock number of teeth. One tooth less on the front sprocket shortens the gearing (more acceleration, ideal on tight terrain); one tooth more lengthens it (more speed on fast tracks). One tooth on the front sprocket is worth roughly three to four teeth on the rear sprocket.

When to replace it?

• Teeth thinned, pointed or hooked.
• Chain that jumps or slaps under acceleration.
• Play between the sprocket and the shaft, or marked splines.

Check it every time you service the chain and replace it along with the rear sprocket and the chain. Many riders change the front sprocket with every new chain, because it wears much faster than the rear sprocket.

Fitting tips

1. Loosen the sprocket nut or bolt while holding the rear wheel with the brake, before slackening the chain.
2. Clean the countershaft and check the oil seal behind the sprocket.
3. Fit the sprocket the right way round, with a lock washer or threadlocker as on the original assembly, and tighten to the manufacturer's torque.
4. Set the chain tension and lube it with chain lube.

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

• Rear sprocket : RENTHAL · INNTECK
• Drive chain : AFAM A428MX-G 1 · AFAM A420R1-G
• Chain lube : LIQUI MOLY 400 ml · MUC OFF

Frequently asked questions

Should the rear sprocket be changed too?
If it's worn, yes: a new front sprocket running on a tired rear sprocket and chain is worn out within a few hours.

Compatibility

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

Fits:
KTM SX 85 2017
KTM SX 85 2016
KTM SX 85 2015
KTM SX 85 2014
KTM SX 85 2013
KTM SX 85 2012
KTM SX 85 2011
KTM SX 85 2010
KTM SX 85 2009
KTM SX 85 2008
KTM SX 85 2007
KTM SX 85 2006
KTM SX 85 2005
KTM SX 85 2004
KTM SX 85 2003