How to Tighten the Chain on a Yamaha Raptorby Chris Gilliland
While most ATVs rely on a shaft-driven transmission, Yamaha's Raptor 660 uses a chain and sprocket drive system to power it over rough terrain. As the Raptor was designed primarily as a sporting machine, the use of a chain allows its rider to quickly change the ATV's acceleration and speed by swapping either or both sprockets. However, the chain will stretch over time and eventually slip off the sprockets. To prevent this, a set of chain adjusters built into the rear swingarm is used to return the chain to an optimal tension for most riding environments.
Lift the ATV's rear wheels off of the ground, using a jack placed below the engine. Support the ATV's frame with jack stands.
Grasp the chain's upper strand between the front and rear sprockets. Measure the chain's slack, using a ruler or tape measure, by pushing down firmly on the chain, then lifting the chain as far as it will move. Ideally, the chain must have a range of motion between 1.18 inches to 1.77 inches.
Spin the rear wheels until the hub nuts on the right side of the rear swingarm are visible through the holes cut into the rear brake disc. Loosen the hub nuts, using a socket wrench an a 14 mm socket.
Loosen the chain adjuster lock nuts on both sides of the rear swingarm, facing the engine, using a 12 mm crescent wrench.
Turn both chain adjuster bolts, using a socket wrench and a 12 mm socket clockwise to loosen the chain, or counterclockwise to tighten the chain. Turn the bolts in even amounts to keep the rear wheels aligned. Check the chain slack periodically, as described above, and make adjustments until the chain slack is between 1.18 inches to 1.77 inches.
Check the rear wheel alignment, using the alignment notches cut into both sides of the swingarm and both rear axle hubs. Adjust the tightest side of the rear axle, using the chain adjuster bolts, until both rear axle hub notches are aligned with the corresponding swingarm notch.
Check the chain slack again, as described above. Tighten the chain adjuster lock nuts against the swingarm, using a 12 mm crescent wrench, if the chain slack is between 1.18 inches to 1.77 inches. Adjust the chain, as needed, if the chain slack is not within the specified range.
Tighten the rear hub nuts to 65 foot-pounds, using a torque wrench and a 14 mm socket.
Remove the jack stand and lower the ATV's rear wheel to the ground.
- Replace the chain and both sprockets, if the chain cannot be tightened to the specified chain slack range. This is a sign that the chain has been stretched beyond its serviceable range, increasing the odds of the chain snapping while the ATV is in operation.
- Do not operate your Raptor 660, if any of the chain links are bound or stuck together. The chain must be able to move freely to prevent the chain from slipping off of the sprockets.
Items you will need
- Jack stands
- Ruler or tape measure
- Socket wrench
- 14 mm socket
- 12 mm box wrench
- 12 mm crescent wrench
- Torque wrench
- "Yamaha YFM660RN/RNC Service Manual"; Yamaha Motor Corp.; 2001