You see a crack in a frame tube, at a weld, at the steering head, at an engine mount, in the rear subframe or in a bracket for a footpeg, stand, carrier or seat. Cracks start from overloading (heavy cargo, passengers), crashes, potholes, vibration from loose engine mounts, or rust. A crack grows with every ride and can break suddenly.
Is it safe to ride?
No, if the crack is in the main frame, steering head, swingarm, engine mounts or subframe. A small crack in a non-structural bracket (for example a panel tab) is less urgent, but have it checked.
Quick checks first
- Clean the area and look with a torch. Paint that is cracked in a line, rust streaks or a black line at a weld can hide a crack.
- Is anything bolted to the cracked part loose?
- Has the bike carried very heavy loads, or been in a crash?
Diagnose it step by step
1Where is the crack?
- Main frame, steering head, swingarm, engine mount, subframe: do not ride. Go to step 4.
- Bracket for a footpeg, stand, seat, carrier or panel: go to step 2.
2Is the part held by the bracket loose, or has it been loose for some time?
- Yes: a loose part hammers its bracket. After repair, tighten it to the correct value and check it often (Check chassis fasteners).
- No: go to step 3.
3Is the crack only in paint, or in the metal? Clean to bare metal or ask a workshop to dye-test it.
- Paint only: touch up and watch it.
- Metal: the bracket must be replaced or repaired by a competent welder. Remove the fuel tank and battery before any welding nearby.
4Was the bike in a crash or hit something hard?
- Yes: the frame may also be bent. See The bike has been dropped or crashed and Inspect the frame after a crash.
- No: go to step 5.
5Are the engine mounts tight, and has the bike carried heavy loads?
- Loose mounts: Check engine mounting bolts. Loose mounts let the engine shake the frame.
- Heavy loads: keep loads within the maker's limit, and use a carrier designed for the bike.
6Workshop decision:
- A frame specialist decides if a steel frame can be repaired, and checks alignment after. Aluminium frames are usually replaced. Do not ride until it is repaired and checked.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Loose part hammering a bracket | Bolts loose, crack at mount | New bracket, tighten |
| Overloading | Crack at subframe or carrier mounts | Workshop repair, reduce load |
| Crash or pothole | Crack plus bent parts | Crash inspection |
| Loose engine mounts | Mount bolts loose, vibration | Engine mounts |
| Rust | Crack in rusted area | Workshop repair or new frame |