It's 27 MM. Buy a product called (Ride On). it's a tire sealer and balancer. Much better than slime, will not dry out, and much smoother out on the open road. I have never had a flat with it!
P.S. This is the same size socket as the large nut on the variator. I would buy an impact version, buy a cheap electric impact wrench from harbor frieght or else where, and change your own belts, rollers etc.
Good luck.
