Replacing The Drive Chain
The chain will naturally stretch as it wears. On a non-sealed chain this should not exceed 3% of its original length. Sealed chain stretch should not exceed 1% of its original length. If the stretch exceeds this it needs to be replaced.
A drive chain that carries too much tensions speeds up wear by excessive amounts of pressure being placed on the sprocket teeth, chain joints and the gearbox main-shaft bearings. One that is too loose is at risk of a whip action that may cause it to snap. Having an incorrect tension can also cause the chain to stretch.
Normal sag is 3/4"; to check, press down on the top strand of the drive chain with your fingers. Tighten or loosen to achieve the desired sag. Note this should be performed with the weight of the rider on the bike. It is advised to check your manufacturer's handbook for your particular machine.
Misaligned sprockets can greatly reduce chain and sprocket life. Check sprocket alignment periodically to ensure they are straight.
Maintenance of Sealed Chains
External lubrication is recommended every 300 miles. Use paraffin oil for washing the chain, but never use steam, thinners or solvents. If any seal rings are missing then the entire length of chain should be replaced.
'Press fit' rivet link side plates must be pressed on with long-handled adjustable pliers. Do not attempt to hammer the side plate on! This can cause stress to the connecting link and cause it to break through use. Rivet links should always be fitted with the correct Press Fit tool, which will avoid any damage to the rivet link. If you are unsure we recommend you consult a professional workshop.
When To Replace
Bruises, rust, stiffness, damaged O-rings and any other visible damage may cause the chain to break. If any of these are discovered, as well as abnormal noise during use, or stretching, the chain and sprockets will need to be replaced.
If battery acid/liquid is spilt on the chain the whole chain will also need to be replaced.
Some bikes, such as Yamaha R1's, can have a chain conversion from a 50 to a 520. This can be useful if you desire a lighter chain. Other bikes can have a chain conversion from 520 to 50, for extra durability.