A Kawasaki KLX150 with a noisy chain is usually too slack, packed with dried mud or running on worn sprockets. Because the suspension moves through a long stroke, the slack setting has to be right through that travel, not just at rest.
Before you start
A chain that jumps a tooth can lock the rear wheel mid-corner. Never inspect a moving chain, never reach near the sprocket with the engine running, and fit the master-link clip in the correct direction.
Machine file Kawasaki KLX150
- Engine
- Air-cooled SOHC single
- Cooling
- Air
- Fuel
- Carburettor
- Transmission
- Five-speed manual
- Final drive
- Chain
Slack through the stroke
A dual-sport swingarm moves a long way, and the chain tightens as the suspension compresses. Set the slack with the bike in the position the manual specifies, then check that the chain still has a little movement when the rear is pushed down.
Too little slack at rest becomes a locked chain at full compression, which loads the output bearing and can snap a link. Too much lets the chain jump the sprocket on a bumpy climb, and that can lock the rear wheel.
Noise and the part to check
| Noise | When | Check |
|---|---|---|
| Rattle over bumps | Rough ground | Chain slack |
| Rhythmic tick | Once per wheel turn | Seized link |
| Grinding in mud | After a wet ride | Slider and sprocket |
| Scrape under power | Climbing | Sprocket teeth |
| Buzz at one speed | Steady throttle | Guide bolts |
| Clunk over bumps | Landings | Suspension pivot |
Mud, grit and dried clay
Trail mud dries into a hard paste around the chain, the front sprocket and the slider. That paste holds grit against the rollers and grinds the chain from the inside, which is why a mud-covered chain wears faster than a dry one.
Clean the chain with a brush and a suitable cleaner, then lubricate it while it is still slightly warm from a ride. A pressure washer drives water past the O-rings, so use low pressure and keep the nozzle moving.
Tight links after water
Water crossings and rain wash lubricant out of the rollers. A link that dries out seizes, and a seized link produces a rhythmic tick once per wheel revolution and cannot be freed by lubricant alone.
Rotate the wheel slowly and watch each link pass the sprocket. If one stays straight while the rest bend, the chain is at the end of its life. Replace it before it damages the sprockets.
Sprockets and gearing changes
Off-road riding wears the rear sprocket quickly because mud acts as an abrasive. Hooked teeth let the chain ride high in the valley, and the noise becomes a scrape under load.
If a previous owner changed gearing for trail use, check that the chain length matches the new sprocket sizes. A chain that is too short for the set cannot be adjusted correctly and will always run too tight.
The slider and the guide
The chain runs over a rubber slider on the swingarm and through a guide near the front sprocket. Mud wears the slider fast, and once it is through, the chain cuts into the aluminium swingarm.
Inspect the slider for depth and the guide for cracks. Replacing a slider is cheap; repairing a grooved swingarm is not. Check the mounting bolts while you are there, because a loose guide buzzes at one particular speed.
Noise that is not the chain
A clunk over bumps may be a worn suspension pivot, and a rumble that follows road speed may be a wheel bearing. Both are common on a bike that has been ridden in water and grit.
Spin the rear wheel with the engine off and listen at the hub. Lift the rear and check for play. If the noise survives a clean, a lubricated chain and a correct adjustment, look at the bearings next.
Keeping it from coming back
Off-road chain life depends on cleaning and adjustment through the suspension stroke. Measure slack in the manual's position, clean dried mud after every ride, and check the slider and guide. Use low pressure when washing so water does not pass the O-rings. Replace the set when the teeth hook or a link will not flex.
A short checklist
- Measure slack with the bike in the manual's position.
- Push the rear down and recheck slack through the stroke.
- Clean dried mud from the chain and front sprocket.
- Rotate the wheel and look for tight links.
- Inspect the slider, guide and sprocket teeth.
- Check for wheel bearing play with the rear lifted.
Questions owners ask
Why does my KLX150 chain get tight when I sit on it?
The swingarm arc tightens the chain as the suspension compresses. Slack must be set so the chain still has movement at full compression; a setting that looks right at rest can be too tight when ridden.
How often should I clean an off-road chain?
After every muddy or wet ride. Dirt holds moisture against the rollers and dries into an abrasive paste, so cleaning and lubricating after the ride is more effective than waiting for a service.
Can I use a pressure washer on the chain?
Only at low pressure and never held in one place. High pressure forces water past the O-rings and washes out the lubricant, which is how a chain seizes in a few weeks.
