14 mm decompressor Valve

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rudge250
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14 mm decompressor Valve

Postby rudge250 » Tue Dec 05, 2017 4:38 pm

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
:D :NSW:
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
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Posts: 11
Joined: Mon Nov 20, 2017 8:57 am
Bike: Montesa

Re: 14 mm decompressor Valve

Postby rudge250 » Wed Dec 06, 2017 4:04 pm

:NSW: :D 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 ?



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OlDaz
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Re: 14 mm decompressor Valve

Postby OlDaz » Wed Jan 24, 2018 3:20 pm

"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.


Still remembering when.....


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