Billy, I was racking my brain to remember what it was called. Yes, Hall Sensor. Thanks for that.It's a hall sensor, which means it's magnetic hence it picks up swarf. Google how to test a hall sensor. Hope this helps .
If you have a mate who has a Harley, you could do a quick swap which would prove yours is bad.It's an 05 springer softail with carb conversion
A reasonable replacement sensor is about 70 quid , but that's the offset to owning a Harley.
The hall effect sensor has a AC 5 volt induced value from a segmented toothed ring which tells the ecm when to induce a spark.
Guess I might just have to bite the bullet