According to the Yamaha Parts Catalog online you need
Yamaha Part # 94701-00333-00, SPARK PLUG
NGK Standard DR8EA #7162 Gap .024
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Hope This Helps.
Use NGK MOdel # d7ea WITH A GAP SIZE OF 0.028
18MM
When changing the spark plugs of an engine, a person should leave the right gap size. The Spark plug gap size of this engine would be .39 inches
400 cc Yamaha engine
11/16inch or 18mm socket.
The following spark plugs are specified for a 1990-1999 Yamaha RT-100: NGK B7ES (or if you want to upgrade to iridium, BR7EIX) Denso W22ES-U (for the iridium version, IW22) FYI, the spark plug gap is .022"
Spark plug setting should be at .31
what is the spark plug gap size for a 1987 suzuki savage 650?
18 mm spark plug socket
the spark plug gap size on a Mercedes e420 is .32
.035 gap. DPR8ea-9 spark plug
You need an 18 mm spark plug socket.