Easy question

[FFRDave]

What is the thread pitch and diameter for a Gas gas Motorcycle spark-plug?

Here is why I am asking.
I had a heck of a time threading my compression tester into the spark plug hole under my tank. I found myself wishing for an elbow of some sort that could act as a 90 degree adapter, so I could thread my tester on from the side.

I have decided that I can make one if I know what threads I need. All the adapters in my compression tester kit are streight, but of various sizes. Does anybody already already have one of these adapters, available for purchase
?

It may be as simple as going to a hardware store and buying a 90 degree plumbing fitting.

Its just an idea....

[RBD]

The thread size is a 14 X 1.25 (14 millimeter diameter by 1 thread every 1.25 millimeters.

This is not a common thread size other than spark plug use.

I think your 90* adaptor is a good idea, but it would take some doing to make it work properly. The biggest thing would be to make the female thread swivel around 360* once the adaptor is installed and sealed to the head. This way you could swivel the threaded hole (where you actually hook up the compression tester) to any position you want, so it won't possibly be pointing at an obstruction.

Ron

[FFRDave]

Could it have a lock-nut with an O-ring on its base to make the seal to the spark-plug hole (like a clutch cable adjuster nut)?

This way, the adapter could be positioned any way the user wanted, but the lock nut would put pressure on an O-Ring to provide the seal to the head. Then, the 90 would also have to have a flat surface for the Compression tester O-Ring to seal to. A drilled and tapped hole in the side would not do.



And now a question for everybody:

If something like this were available, would you want one?

[Gonzo]

I reckon an adapter with a braided steel hose mid section [Am I making sense?] might be a better idea. That way you've not got to worry about obstructions as you'd be able to screw the tester into a flexible end. Dunno how you'd go about it though.