Bike feels held back, as if something is dragging

The engine sounds normal, but the bike is slow to pick up speed, slows quickly when you close the throttle, and is heavy to push. Fuel use often rises too. Something is resisting the wheels: a brake that does not fully release, a tight chain, a failing wheel bearing, or a soft tyre. The K-Light 125 fault charts for low power and high fuel use both start with this check.

Is it safe to ride?

With care, and only after the checks below. If a brake disc, drum or hub is very hot after a short ride, or a wheel is hard to turn, do not ride: a dragging brake can overheat, fade or lock.

Quick checks first

• Push the bike in neutral with the engine off. Is it harder than usual?
• Are the tyres at the right pressure, with no slow puncture?
• After a short ride, is one brake disc or drum much hotter than the other? Test carefully by holding your hand near it first.
• Is the chain very tight?
• Do the brake lever and pedal have their normal free play?

Diagnose it step by step

1Put the bike on its stand and lift each wheel off the ground in turn. Give it a firm spin. Does it turn freely for several turns?

• Yes, both: go to step 4.
• No, one wheel stops quickly or rubs: go to step 2.

2Release the brake fully. Is the brake rubbing?

• Disc brake: you hear a constant scrape and the disc is hot. Check for brake drag, then clean the caliper and free the pistons. See Brake caliper sticks or is seized.
• Drum brake: the shoes rub if adjusted too tight or the cam sticks. Adjust the drum brake.
• Rear brake pedal with no free play, or a linked brake (CBS) that stays partly on: Adjust the rear brake pedal. On the K-Light 125 the rear pushrod must have a small clearance so the master cylinder piston returns fully; if not, both rear and the linked front brake drag. Linked brake faults: Check a combined braking system.
• Brake is not touching: go to step 3.

3With the brake clear, does the wheel feel rough or grumble when turned slowly, or rock on the axle?

• Yes: worn wheel bearings. Check wheel bearings. See Rumbling or grinding from a wheel.
• A spacer missing or the axle over-tightened can also bind the bearings; the K-Light 125 chart lists a missing or short hub spacer.
• No: go to step 4.

4Rear wheel: is the chain too tight, or tight in one spot?

• Yes: Check and adjust chain slack (K-Light 125: 20 to 40 mm, upright). Tight spots: Chain is tight in some places.
• No: go to step 5.

5Are tyre pressures correct?

• No: Check tyre pressure. A tyre that keeps going soft: Tyre slowly loses air.
• Yes, and nothing drags: the engine itself is weak. Go to Engine feels weak and down on power.

Confirm with a road test: the bike should roll freely when you pull the clutch at speed.

Causes, most likely first

Reference values (K-Light 125)