An impact wrench (also called an air gun or rattle gun) hits the socket with many fast blows. It can undo a tight nut, such as a flywheel or clutch nut, without locking the engine, because the blows are too quick for the crankshaft to turn. It is a removal tool. It has far too much power and no feel for tightening motorcycle fasteners.
Safety
- Wear eye protection. Sockets, broken bolts and rust flakes can fly off.
- Use only impact sockets. An ordinary chrome socket can split under the blows and throw pieces.
- Keep fingers away from the socket and the work. The tool kicks when the nut breaks loose.
- Air tools: use a hose and fittings rated for your compressor pressure. Do not point the air line at skin.
You need
- An impact wrench in the right drive size. Small drive sizes suit small fasteners; a large gun can twist a small bolt in half.
- Six point impact sockets that fit the nut snugly: Impact sockets.
- For an air gun, enough air volume. A small compressor may run the gun only for a few seconds. An extra air tank in the line helps.
Steps
- Soak rusty threads with penetrating oil first and wait.
- Check the thread direction. Some nuts are left-hand thread; the manual lists them: Identify bolt strength, thread and locking types.
- Set the tool to reverse (undo). Start on the lowest power setting.
- Push the socket fully onto the nut and hold the tool square to it.
- Give short bursts. If the nut does not move after a few seconds, stop. More hammering can damage threads or a crankshaft key. Try more power, heat or a breaker bar: Undo a stuck or rounded fastener.
- Once loose, you may spin the nut off with the gun, or by hand.
Refitting
- Start every nut and bolt by hand so it cannot cross thread.
- You may run a nut down a long thread with the gun at low power, but stop before it seats.
- Do the final tightening with hand tools and a torque wrench to the value in the manual: Use a torque wrench.
Check your work
- The fastener came off with its thread and head undamaged.
- On refit, every fastener was tightened by hand and torque wrench, not by the gun.
If it did not fix the problem
- Rounded head or broken bolt: Bolt or screw head is rounded or stuck.
- Thread pulled out of the casting: A bolt hole thread is stripped.