Motorcycle Repair: dirt bike reving on its on, reed valves, yz80

Question
i have 1988 yz80 i rebuilt the top end the bike sat up for a couple of years before rebuild i cleaned the carb and put the bike back together it takes a few kicks to get it to start a when it starts it will idle for a few seconds then it revs up on its on until it gets wide open turning the idle screws does not affect it at all i have another carb for the bike and it does the same thing it seems to have plenty compression any advice would be appreciated

Answer
You either have a big air leak in the connection between the carb to the cylinder, or a blown lower cylinder gasket, or you have the slide in the carb installed incorrectly.  The bevelled end goes towards the airfilter.  Do you have the reed valves in correctly?

Let me know,  Jan