A Yamaha R15 with a noisy chain is usually running with incorrect slack, a tight link, worn sprockets or a misaligned rear wheel. The chain is exposed and easy to inspect, provided you measure rather than listen alone.
Before you start
A broken chain can lock the rear wheel. Never inspect a running chain, never reach toward the sprocket with the engine on, and never ride without the master-link clip. Torque the axle nut to the specification.
Machine file Yamaha R15
- Engine
- Liquid-cooled four-valve SOHC single with VVA
- Cooling
- Liquid
- Fuel
- Fuel injection
- Transmission
- Six-speed manual
- Final drive
- Chain
Set the bike up correctly
Chain slack is measured with the suspension at the position the manual specifies, usually on a stand or with the bike upright. Measuring on the side stand changes the reading and leads to a wrong adjustment.
Compare the movement at the midpoint between the sprockets with the manual figure. Too much slack causes slap over bumps; too little loads the countershaft bearing and wears the chain rapidly.
Noise and the part to inspect
| Noise | When | Check |
|---|---|---|
| Slap over bumps | Rough road | Chain slack |
| Rhythmic tick | Once per wheel turn | Tight link |
| Scrape under load | Acceleration | Slider and guide |
| Edge wear on sprocket | Constant | Alignment |
| Whine with speed | Rises with speed | Wheel bearing |
| Squeak over bumps | Bumps only | Linkage |
Tight links and stretch
Turn the rear wheel slowly and watch each link as it passes the sprocket. A link that stays straight while the others bend is seized, and it produces a rhythmic noise once per revolution.
Clean and lubricate the chain and recheck. If the link still will not flex, or the chain can be pulled away from the rear sprocket by more than a little, the chain has reached its limit.
Sprocket condition
Worn rear sprocket teeth hook forward and the chain rides high in the valley. A worn front sprocket is smaller and hidden, but it wears faster because it turns more often and has fewer teeth to share the load.
A worn sprocket ruins a new chain, and a worn chain ruins a new sprocket. Replace them as a set when either shows significant wear.
Alignment after a wheel change
The adjuster marks are a starting point, not a measurement. A rear wheel that sits slightly crooked makes the chain run against the sprocket side, which produces a scrape and edge wear.
Use a straight edge or a string line along the wheel, and torque the axle nut to the specified figure. Recheck slack after tightening, because the axle often moves as it settles.
Noise under acceleration only
A chain that is noisy only when you open the throttle may be too tight, or the slider may be worn so the chain contacts metal under load. Check the slider on the swingarm and the guide near the front sprocket.
A worn rubber slider is cheap to replace and prevents expensive damage to the swingarm. If the chain has been running metal to metal, inspect the swingarm for scoring as well.
Other sources of the same noise
A rhythmic knock that follows road speed can come from a wheel bearing, and a squeak over bumps can come from a dry linkage. Confirm the source before buying a chain and sprocket set.
Spin the rear wheel with the engine off and listen at the hub and at the sprocket. A rumble from the hub is a bearing; a tick at the sprocket is the chain or the teeth.
Keeping it from coming back
Set the slack with the bike as the manual specifies, keep the chain clean and lubricated, and check alignment after every wheel change. The R15's engine revs freely, so a dry or misaligned chain becomes noisy quickly. Replace chain and sprockets as a set when the teeth hook or the chain will not flex.
A short checklist
- Measure slack with the bike as the manual specifies.
- Rotate the wheel and look for tight links.
- Inspect rear and front sprocket teeth.
- Verify alignment with a straight edge.
- Inspect the slider and the front sprocket cover.
- Spin the wheel to rule out a bearing.
Questions owners ask
Why is my R15 chain noisy after a wheel adjustment?
The wheel is probably misaligned or the slack was set with the suspension in the wrong position. Recheck alignment with a straight edge and measure slack as the manual specifies.
Can a tight chain damage the gearbox?
Yes. A chain with no slack loads the countershaft bearing and the output shaft seal every time the suspension compresses. It is a cheap adjustment that prevents an expensive repair.
How do I know when the chain needs replacing?
Look for seized links, hooked sprocket teeth and a chain that can be lifted well away from the rear sprocket. Measure against the manual's wear limit rather than judging by sound.
