A Yamaha XSR155 with a noisy chain is usually running with too much slack, a dry link, a worn sprocket or a misaligned wheel. The chain drive is exposed, so the wear is visible if you know where to look and when to measure.
Before you start
A chain that breaks can lock the rear wheel or injure a leg. Never inspect a running chain, never put fingers near the sprocket with the engine on, and never ride with a missing master-link clip. Torque the axle nut to the specified figure.
Machine file Yamaha XSR155
- Engine
- Liquid-cooled four-valve SOHC single with VVA
- Cooling
- Liquid
- Fuel
- Fuel injection
- Transmission
- Six-speed manual
- Final drive
- Chain
Slack, measured not guessed
Put the bike on its side stand or a paddock stand as the manual specifies, then measure the chain's up-and-down movement at the midpoint between the sprockets. Compare it with the figure in the owner's manual rather than a rule of thumb from another bike.
Too much slack lets the chain slap the swingarm and the frame, which sounds like a rattle over bumps. Too little loads the countershaft bearing and wears the chain quickly. Both are adjustment faults, not worn-out parts.
Noise and the part to inspect
| Noise | When it happens | Check |
|---|---|---|
| Rattle over bumps | Rough road | Chain slack |
| Rhythmic tick | Once per wheel turn | Tight spot or seized link |
| Grinding under load | Acceleration | Slider and guide |
| Scrape at the sprocket | Constant | Alignment and edge wear |
| Whine with speed | Rises with speed | Wheel bearing |
| Squeak over bumps | Bumps only | Linkage or exhaust mount |
Tight spots and dry links
Rotate the rear wheel slowly and watch the chain as it passes. A tight spot stays rigid where the rest of the chain bends, and the noise becomes rhythmic, once per revolution.
A tight spot usually means a seized link caused by dried lubricant or corrosion. Clean and lubricate the chain and recheck; if the link still will not flex, the chain is at the end of its life.
Sprocket teeth
Look at the rear sprocket from behind. Worn teeth hook forward into a shark-fin shape, and the chain sits high in the valley instead of deep in the root. A worn front sprocket is smaller and harder to see, but it wears faster because it turns more often.
A new chain on worn sprockets wears out quickly and runs noisily. A new sprocket with an old chain does the same. Judge the set together, not one part at a time.
Alignment after adjustment
The adjuster marks on the swingarm are a guide, not a precision instrument. A rear wheel that sits slightly crooked makes the chain run against the side of the sprocket, which produces a scraping noise and edge wear.
Use a straight edge or a string line along the rear wheel to confirm alignment, and torque the axle nut to the specified figure. Recheck the slack after tightening, because the adjustment often changes as the axle settles.
Guides, sliders and the front cover
The chain runs over a slider on the swingarm and through a guide near the front sprocket. A worn slider lets the chain contact metal, which produces a grinding noise under load. A missing slider is worse.
Remove the front sprocket cover and check for accumulated grit and a worn guide. That area collects chain lube and road dirt, and a dry chain running through it will always sound rough.
Noise that is not the chain
A rhythmic knock that follows road speed can come from a wheel bearing, and a squeak over bumps can come from a dry suspension linkage or a loose exhaust mount. 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 from the sprocket is the chain or the teeth.
Keeping it from coming back
Chain life on the XSR155 is decided by adjustment and lubrication, not by mileage alone. Measure slack in the position the manual specifies, clean and lubricate after rain, and check the slider and sprocket teeth. A chain that is too tight loads the output bearing; one that is too loose hammers the swingarm and can jump.
A short checklist
- Measure chain slack against the manual figure.
- Rotate the wheel and look for tight spots.
- Inspect rear and front sprocket teeth.
- Check wheel alignment after any adjustment.
- Inspect the slider and the front sprocket cover.
- Spin the wheel to separate chain noise from bearing noise.
Questions owners ask
How often should the XSR155 chain be adjusted?
Check the slack at every service and after any wheel removal. Adjustment depends on wear, not only on distance, so measure rather than following a fixed interval from memory.
Does a noisy chain mean it needs replacing?
Not always. Too much slack, a dry chain or a misaligned wheel can all be noisy with plenty of life left. Look for tight spots, hooked teeth and measured stretch before replacing the set.
Can I use engine oil on the chain?
A proper chain lubricant is formulated to stay on the chain and resist fling. Engine oil spreads quickly and attracts dirt, which increases wear. Use the lubricant the manufacturer recommends.
