What is the best 125cc 2 stroke Dirt bike?

What is wrong with a 125cc 2 stroke dirt bike which starts better than ever all of a sudden but now cuts out after 5 - 10 minutes at high revs?

• Answer:

  Clean the carbs after you check airbox. If your bike starts up and runs great, but then shuts down, it is missing one of the following items: fuel, air or spark. Is your air filter installed properly and is your airbox clean? Did you leave a rag in the airbox by mistake? Don't be embarassed. I have too. If it shuts down five or ten minutes in, I would guess that one of the jets is clogged in the carb. First thing to check: Is fuel flowing freely from the gas tank? Is it possible that some dirt fell into the tank while fueling and is stopping up the fuel hole from the inside? If fuel is flowing freely, run the bike again until it dies and then drain the float bowl in the bottom of the carb with the large nut on the bottom. If fuel flows out, that would indicate that the high speed jet is clogged and needed to be blown out with compressed air. If no fuel flows, somewhere between the petcock and carbs, there is something clogging the line. Get some carb cleaner and dismantle the carb. Keep all the pieces in an ice cube tray and really give them a good once over with a toothbrush. Each jet will need to be blown out to ensure it is working properly. You should check your vent hoses at this time as well, and make sure they are routed properly so they are breathing correctly. Hope this helps. The year of your bike isn't listed, so this is shooting from the hip...