Replace the drain plug sealing washer

Home mechanic (basic tools) · Time: 30 to 45 min (estimate, done with an oil change) (estimate)

A drain plug seals with a crush washer (a soft metal or fibre ring that squashes as you tighten) or an O-ring (a rubber ring). Once squashed, a washer does not seal as well again. A leak at the drain plug usually means an old washer, a damaged seat, a cross-threaded plug or a plug that is too loose or far too tight. On the K-Light the drain is a large "filter spring screw cap" with an O-ring that also holds the strainer screen.

Safety

• A loose drain plug can fall out and empty the engine in seconds. Do not ride with a dripping plug.
• Hot oil burns; let the engine cool enough to handle.
• Wear gloves and catch all the oil.

You need

• The correct new washer or O-ring. Match the inside and outside size and material to the old one. Copper and aluminium washers are not the same size on every bike.
• Fresh oil to refill (easiest to combine with Change the engine oil and clean the strainer).

Steps

1. Clean the area round the plug and confirm the leak really starts at the plug, not from higher up. Use Trace an oil leak if in doubt.
2. Place the tray and remove the plug or cap slowly.
3. Remove the old washer or O-ring. Old crush washers sometimes stick to the engine; peel them off.
4. Wipe the seat on the engine. Look with a torch for cracks, dents or a raised edge round the hole.
5. Look at the plug threads. Flattened or shiny torn threads mean the plug or the case thread is damaged.
6. Fit the new washer or O-ring. Lightly oil an O-ring.
7. Start the plug by hand for several turns. It must turn easily. If it binds, stop and start again straight.
8. Tighten with a torque wrench to the value in your manual. K-Light 125: filter spring screw cap 15 to 30 N·m. Check that your part is this cap before using the value.
9. Refill and check the oil level.

Check your work

• After idling and a short ride, the plug area stays dry.
• The plug turned in smoothly and reached torque without a sudden give.

If it did not fix the problem

• Plug spins without tightening, or threads came out on the plug: the case thread is stripped. Do not ride. A workshop can fit a thread insert or oversize plug.
• Crack round the plug seat: the crankcase may need welding or replacement. See Assess bottom end and internal engine damage.
• Oil appears above the plug: Trace an oil leak.

Reference values (K-Light 125)