New piston + gaskets!

With the engine stripped, I measured the piston diameter with a set of digital-calipers, as with 25k miles on the bike I figured it may have been bored out some and require a larger diameter piston, but this was not the case and it's running the normal 54mm one.

I ordered a Mitaka Racing piston kit, which includes a new top-end bearing for £35.50 delivered. No engine rebuild would be complete without gaskets so I got a Lextek set from Chinese Motorcycle Parts Online on eBay for £19.95 delivered.