You're in luck - bike rent in Kegalle is totally doable and perfect for those winding roads! Just be prepared to haggle a bit and inspect the bike thoroughly (test those brakes!). Most places offer 100-150cc scooters perfect for the terrain. Found a decent comparison of options here:
https://getrentacar.com/en-US/motorcycle-rental/sri-lanka-kegalle . Remember - the horn is your best friend on Sri Lankan roads!