You will probably always feel the gears engage. The gearbox on this bike is 1950's technology, scaled up from the 200cc Tiger Cub.. I remember my own T100c had almost no ratchet "click" as I went through the gears, but I could feel the engagement and know I had actually shifted.  I am curious about the synthetic oil. First I like synthetics, but had a bad time with Golden Spectro. The clutch plates would stick together(severely). Not while riding but while sitting. When I would start the bike, 1st gear could not be engaged. I could only free the clutch by putting it in gear and rocking the bike while holding the clutch in. Have you had any trouble like this? If you are getting clean shifts and can find neutral at a stop light. All is probably well.