Chain adjustment is a ten-minute job that riders get wrong in two expensive directions — and one of them, over-tightening, is far worse than the sin it tries to fix. Here's the full procedure and the reasoning, so the numbers make sense on your specific bike.
Know your spec first
Slack specs vary hugely by bike because they're really about suspension travel. A sportbike might call for 25–35mm of vertical play; a motocross bike can want 55mm or more. The chain must have enough slack that when the suspension compresses and the swingarm pivot, countershaft, and rear axle align, the chain doesn't go guitar-string tight. Use the number in your manual, measured where the manual says to measure it — usually midway along the lower run, often with the bike on its side stand or with weight specifics.
Measure honestly
Push the chain down at the midpoint, mark the position, lift it up, measure total vertical travel. Rotate the wheel and measure at several spots — chains wear unevenly, and you must set slack at the tightest point. If tight and loose spots differ dramatically, stop adjusting: that's a worn-out chain, and no adjustment fixes it.
The adjustment itself
Loosen the axle nut just enough that the axle can move. Turn the adjusters at the swingarm ends in small, equal increments — a quarter turn or one flat at a time, alternating sides. Most swingarms have alignment marks; treat them as approximate, since they're often slightly off from the factory. String-line the wheel or measure adjuster block to swingarm-end distance on both sides if you want real alignment. A crooked rear wheel wears the chain and both sprockets on one side and makes the bike track subtly wrong.
Torque and re-check
Tighten the axle nut to spec — this matters, because an under-torqued axle lets the wheel walk forward and your fresh adjustment vanish. Then re-measure slack, because tightening the axle often changes it slightly. Spin the wheel, confirm smooth movement, done.
Why over-tight is the killer
A too-loose chain slaps, accelerates sloppily, and in extreme cases can derail. Bad. But a too-tight chain binds every time the suspension compresses, hammering the countershaft bearing — a repair measured in engine disassembly — while stretching the chain and grinding the sprockets continuously. If you must err, err loose within reason. Tight chains also run hotter, which cooks the O-ring grease.
When adjustment becomes a symptom
Adjusting occasionally is maintenance. Adjusting every other week is diagnosis: the chain is stretching because it's worn, or it's wearing fast because it's running gritty and dry. Grit is the accelerant — the fix is the boring one, a real cleaning habit. The 60-second method with a wrap-around brush like the CC360 makes that habit cheap enough to keep, and the interval guide tells you how often. Adjust less by cleaning more.
Quick answers
How much slack should a motorcycle chain have?
Most street bikes call for roughly 25–35mm of vertical play at the midpoint of the lower run; dirt bikes typically need much more, often 45–60mm, because of suspension travel. Always use your model's manual spec.
Is a tight chain worse than a loose chain?
Generally yes. An over-tight chain binds as the suspension compresses, overloading the countershaft bearing and stretching the chain rapidly. A slightly loose chain is safer than a slightly tight one.
Why does my chain keep getting loose?
Frequent re-adjustment usually means the chain has stretched to its wear limit, or the axle isn't being torqued properly and is walking forward. Check wear before adjusting again.