Rear Spindle Nut Cover

Drill a hole, then use a screwdriver as a drift to force it off !!!

Or angle grinder ???

 

Not just push fit ?

 

One possibility is it twists on, with an expanding part inside
I am sure you have tried but a good counter clockwise twist?

 

Someone asked this a few months ago, is it a grub screw?
Edit .I wrong.

https://www.triumphrat.net/speed-triple-forum/139454-09-speed-triple-rear-axle-covers-2.html

 

https://www.ebay.com/itm/Triumph-Sp...Plug-Kit-Black-/302938645121?oid=302628549709

Looks similar to this one on eBay
If so, undo the hexagonal bolt on the other side of the spindle

 

I thought they were a push fit with a retaining grub screw.

 

https://www.triumphrat.net/speed-triple-forum/139454-09-speed-triple-rear-axle-covers-2.html

 

Is this it Foxy?
https://www.triumphparts.gbr.cc/product.php/6885879/

They might still be in business and know the answer.......

 

you undo it from the other side
https://www.triumphrat.net/sprint-forum/213385-question-triumph-axle-nut-cover-removal.html

If you are removing the wheel this is the only side you need to remove

 

turn the outer anti-clockwise which should slacken it, then just prise out with a couple of screwdrivers

 

Tap it out from the other side

 

What can you see from the other side?
Shine a torch and hopefully the fixing type will be identified

Of course I am sure you have done this but just covering all the bases