You set the chain tension, turn the pedals, and suddenly it feels different: tight here, loose farther around. Checking only where the cranks happen to stop can hide the problem. Before adjusting again, compare the tightest and loosest positions through a complete circuit of the chain.
This check is for a chain-driven setup without a derailleur managing chain slack. It is not a belt-tension procedure, and tightening caused by rear suspension movement needs a different inspection.
Check a full circuit, not one pedal turn
Switch your electric bike off and follow its battery-disconnection instructions. Support it securely with the driven wheel clear, using equipment suitable for its weight. If you cannot do that safely, leave this check to a shop.
Turn the cranks slowly by hand, keeping fingers, sleeves, and tools away from the chain and teeth. Stop immediately if the drivetrain binds. Do not use motor power to push it through a tight position.
Stop all movement before gently checking up-and-down chain movement at the midpoint of the same free span between the sprockets. Use similar light pressure each time. Move your hand away, advance the chain, stop, and compare again.
One crank revolution is not necessarily one complete chain circuit. If there is an identifiable joining link, watch until it returns to its starting point. Do not attach string, tape, or anything loose as a marker. You are comparing different chain sections at the same checking location, not pushing on different places along the span.
Notice what the tight spot follows
Does the change repeat near the same crank position? Or does a particular link stay kinked as it leaves a sprocket and enters the straight span? Note the pattern before making an adjustment.
A repeating change can involve how evenly the sprockets run; a link that does not straighten calls for inspection of that link. Neither observation proves that the front chainring needs replacement. Chain condition and the rear sprocket also matter, and more than one issue can be present.
If this began after a new chain or rear-wheel work, say so. A short, power-off video of the repeating pattern can be useful, provided someone else records it and everyone stays clear of moving parts.
Do not fix the loose spot by overtightening
The tightest position must still meet the bike or drivetrain maker's tension guidance without binding. But the looser positions must also retain the chain properly. Do not use a generic finger-width gap as a substitute for those instructions.
If removing the slack makes another position bind, stop adjusting and have the chain, sprockets, and their mounting checked. Do not knock a chainring into alignment or reposition a hub-motor axle and its hardware by guesswork.
If the symptom is skipping under pedaling rather than this repeating tension change, our chain-slipping guide covers the wider causes. For this problem, the useful endpoint is a chain that runs freely and stays engaged throughout its circuit, not one position that feels right.
