Today after about an hour and half of riding country roads I ended coming back closer to home and was at a traffic light. I took off fine but not long after shifting into third hitting around 60km/h my the bike jolted forward a bit two or three times; each time the tacho needle dropped instantly done to around 0 then back up again. About 2 minutes later I cut the throttle and it did it again once. Yet the rest of the ride home was absolutely fine including some highway driving. Does anyone know what would cause this and is this something that could happen again? The only thing I could think of with my very limited knowledge was something wrong with the ignition so I checked the battery and it's reading 12.8v so that at least should be fine.