That’s a carburetion problem. You don’t see it too often but it happens in a certain series of turns/straights with some set ups. The track empties out the crank case and you open the throttle too fast and no fuel. Usually a long straight tight turn short straight another turn and when you get on it nothing.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience