How to adjust speed sensor

[Hairsy16]

I have a problem with my speedo - it stops working when the brakes get hot on track. I can easily see that the gap gets bigger due to the different expansion rates of the components.

The gap looks to be too large so I need to close it up. That should be simple but I can't work out how to turn the speed sensor to make the adjustment.

There is nothing to 'grip' the sensor and turn it.

Can anyone advise how to make the adjustment - pics below ...

Thanks

Dave

[Hairsy16]

Really? Oh what a pain. £100 doesn't seem worth it when its only on track. Was really hoping I was missing something obvious.