i see. well actually that's my plan to change to 90/80 rear, it's just that my rear tire is still new, (sayang kasi). i,m quite heavier than you i'm 84kg and i also did hard break-in.Sir,
nag 130KPH ako using UMA Digital Speedometer. around 122km/hr on GPS. Used break in method by motoman which is used by Sir Traxxis.
Engine, exhaust and Sprocket all stock
changed tires to 90/80 rear, 80/80 front FDR Sports XR Evo. Removed the tube (interior) and my rear wheel is almost 2kgs lighter. I believe the hard break in and lightening of the rear wheel contributes a lot. I am also using RB footrest v4. I all weighed the tires and rearset and a saved 5kgs. My weight is 60kgs.
Imagine your rear wheel is 2kgs lighter multiplied several thousand times.
I was just having 120kph using stock tires and mineral oil.
Planning to reduce 5-10kg of my weight and who knows i can reach 130kph on GPS all stock.