Q&A for How to Gap a Spark Plug

Yes. Add more to get the right thickness, if your thickest leaf is too small. It's a very accurate way to measure or set a gap.

It says on the inside flap of the box whether or not they're pre-gapped.

NGK offers an extensive pocket book, which is often given away for free at exhibitions and motor fair. You can usually find this sort of information on NKG's website as well. The correct gap depends on the motor type and may vary from the gap when buying it new.

The distance of the gap between the center electrode and the side electrode is measured in thousandths of an inch.

It depends on the plug. Consult the owner's manual -- they will usually spec the plug and gap in the maintenance section. If you don't have the owner's manual, you may be able to download it for free -- manuals.lib has an extensive inventory.

Your owners manual should list the gap size in the back of the book; if you don’t have an owners manual, you may be able to download one online for free.

It isn't necessary if the plug leads are in good working condition, but people often renew them when doing a plug change to be sure. you can ask a mechanic to check the resistance of your leads. It's an easy test, and shouldn't cost you.

Disconnect battery lead. Set the engine to top dead center by turning the crank shaft pulley clockwise. The crankshaft pulley has a mark or groove on the edge; line this up with the pointer or mark on the timing cover. When you remove your distributor cap, the rotor should be pointing where the lead to #1 cylinder would sit. If not, turn engine another revolution. When you have rotor pointing to right spot and engine set to TDC mark where the rotor points with a dot of paint. Undo distributor bolt and wiggle it up and out. Refit with rotor pointing to paint spot.

It depends on the tool you are using. Auto stores will sell what looks like a half dollar coin with a hole at the top. That’s not to put on your key chain, it’s actually how you will gap your spark plugs. Put the ground strap in that hole and push down. If you are using the plastic round gap tool, then on the side where it’s shaped oddly, put one side of that in between the ground strap and electrode (making sure you do not brake the electrode). Push back until the desired gap is achieved.

If your finger can fit between the chainsaw and the base of the tree, then you need a new chainsaw.

1 gap per plug is usually the safest though 2 or 3 gaps can be used in some situations, depending on the definition of gap at the time.