NGK Spark Plug CR6EH-9 - Montesa 4RT

4RT Spark Plug
NGK park number: CR6EH-9

The standard spark plug for the Montesa Cota 4RT, including the Repsol and 300RR models.

C - Thread Diameter 10mm
R - Resistor Type
6 - Heat range
EH - Partial Thread, Total reach 19mm (3/4"), Total thread 12.7mm (1/2")
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9 - Wide Gap setting 0.9mm (0.035")

Spanner Hex size 16mm (5/8")

The plug has tapered shoulder which I assume helps with the sealing and cooling of the plug via heat transfer to the cylinder head.

NGK Stock Code 2688