Place the motorcycle on the side stand with no rider or luggage. Check the total vertical slop in the chain at a point about 30cm forward from the rear axle.
- F750GS: 30-40mm
- F850GS: 40-50mm
(When correctly set, the top of the chain will hit the swingarm guard when deflected upwards.)
If the tension needs to be adjusted, loosen the axle nut with a 36mm wrench, then adjust the adjusters on both sides of the axle. Tighten the axle nut to 100Nm with thread locker.
The factory sprockets have 17 teeth in the front and 44 in the rear. The factory chain has 122 links with a pitch of 525.
You will also need a replacement bolt for the swingarm pivot. The part
number is 33 35 8389087.
Note that the bike should be in first gear during the replacement procedure. The procedure requires disconnecting the shifter linkage, so changing gears mid-procedure may be difficult.
See rear wheel removal instructions to remove the rear wheel and the rear sprocket carrier.
Remove the rivet and screws securing the chain guard to the swingarm.
Disconnect the quickshifter (if installed) and unclip the top end of the shifter linkage.
Unbolt and remove the left rearset. This allows access to the front sprocket.
Remove the front sprocket from the output shaft along with the chain.
Inspect the condition of the guard that protects the engine case in case of a chain snap. Replace if necessary, taking care that the sidestand killswitch wire and and breather hoses are correctly routed.
Apply high-temperature anti-seize to the transmission output shaft.
Thread the new chain over the new front sprocket and install the new front sprocket on the output shaft.
Remove the rear sprocket carrier assembly and the spacer bushing from the rear wheel.
Use a 19mm socket to remove the nuts securing the sprocket to the carrier. Install the new sprocket to the carrier, torquing the nuts to 110Nm with thread locker.
Remove the dampener element from the rear wheel. Inspect the condition of the dampener and replace if damaged or deformed. Use silicone spray lubricant when re-installing the dampener.
Clean the spacer bushing and lubricate it with a high-temperature lithium grease.
Reinstall the rear sprocket carrier assembly and spacer bushing.
Reinstall the rear wheel loosely.
Reinstall the bolt for the front sprocket, making care that the washer’s curve faces outward. Torque to 50 Nm.
Reinstall the left rearset. The central M20 bolt must be replaced with a new bolt and the new bolt torqued to 200 Nm. Torque the M8 screws to 28 Nm and the M10 screws to 38Nm.
Reconnect the shifter linkage and quickshifter connector.
Reinstall the chain guard. Use thread locker on the screws.
Lower the bike onto the ground and adjust the chain tension.