14 mm decompressor Valve

[rudge250]

try as I may I cannot find any information on adapting a 14 mm Valve to the threaded spare hole in the Cylinder head of my 247 T Cota. The Head thread hole is approximately 11 mm and probably Metric. Will it safely tap out to 14 MM ?
Or is an adaptor available somewhere ?. Thanks Sean

P.S After many hours the Electrics are now working, were a total mess !!! Speedo opened and repaired, waiting for a Cable from the UK. Chain Guard on order fro Germany ,, metal.

[rudge250]

Hole taped out to 14 mm ok. made a tap from an old Spark Plug. Apparently the thread pitch is not std. and peculiar to 14 mm plugs ,so says internet search ?

[OlDaz]

"Standard" M14 as used for bolts has 1.5mm pitch, spark plug is M14 x 1.25 which is a standard metric fine thread.

If you have a stripped spark plug hole, the repair kit uses a 1.25mm pitch tap that uses the original threads as a guide, then you wind in the stainless insert to get you back to M14 x 1.25 thread.

The second hole on my 247 was stripped sometime in the past and plugged with a custom M12 "plug" to seal it - I'm considering repairing this thread to fit a decompressor with M14 x 1.25 (spark plug thread) while I have the engine apart.