HI there all, i have a H reg DT 50 MX The bike starts and i can ride for a few miles then dies and wont start again. ive stripped carb and cleaned and cleaned valve float needle and cleaned spark plug and there is a a spark.

can anyone help

Fuel starvation? Maybe the tank vent is blocked so a vacuum builds up in the tank, stopping the fuel getting out. Simplest way to check is to run the bike with the tank cap open, see what happens.