Two-stroke engines vibrate enough to undo standard fasteners over time. Petrol edgers in particular have hundreds of small bolts, and a few key ones that you really don't want to come loose mid-job.

The fasteners we see fail most often, in order of how much trouble they cause:

1. Blade retaining bolt. The single most important bolt on the whole edger. If this works loose mid-cut, the blade departs sideways at high speed. Check tight before every use. Use the manufacturer's torque spec if you can find it.
2. Engine mounting bolts. Hold the engine to the chassis. Loose engine bolts cause vibration to get worse, which makes more things loose, snowballing.
3. Handle bar bolts. Loose handle bars feel awful and the wobble can throw your back out over a long job.
4. Cover screws. Air filter covers, recoil starter covers, cylinder covers. Lose one and you'll never find a replacement that fits perfectly.
5. Wheel axle bolts. Wheel comes off mid-job, edger digs into your lawn, scratch in your concrete from the metal axle dragging.

What to do about it:

• Use threadlock on critical bolts. A drop of blue Loctite (242) on the threads of the blade bolt and engine mount bolts. Stops them backing out. Blue is removable, red is not, use blue.
• Spring washers and Nyloc nuts. Where the original assembly used them, replace them when they wear out. They're there for a reason.
• Check critical bolts regularly. Blade bolt before every use. Engine and handle bolts at the start of each season. Cover screws whenever you have the cover off.
• Don't over-tighten. Stripping the threads on a soft alloy housing is a much bigger problem than a bolt working loose. Snug, then a bit more, not gorilla-tight.

One last tip. Keep a small bag of spare bolts and washers for your edger. When you do find one missing, you can replace it on the spot rather than having to put the job on hold while you go to the shop. Most bolts are cheap M5, M6 or M8. A 50-bolt assortment is $10 from any auto shop.