I have a 1975 Yamaha Dt125 the petcock was giving me problems, got that fixed but when I turn the fuel on it seems like the float isn't letting fuel get by the needle valve, I even removed the gas cap to vent it. 

Did you rebuild the carb?

Should be an obvious problem really, so pull the carb off & remove the bowl then hold the carb in your hand over a bucket or something & see if it flows. If not then go looking. Take the float off & needle out & try again. If still none then take out the needle seat. Just work backwards like that. "Then if ya like me" you'll get right up to the tap [fuel cock] & find you haven't put any fuel in the tank. Have a happy dayyyy. ps, is the float upside down. Doesn't have those black plastic floats? i guess as they were a favourite trick for being fitted upside-down stopping any flow.   

Does the petcock have the plastic tapered piece--if so it might be easy to fit that half a turn out & only get fuel flow at random angles of the lever like in between where on & reserve are. If it has one like a DT1 with the flat faced rubber pad then can't easily go wrong in there.

Just curious "why it seems like" it's not getting past float valve?  Clear fuel line perhaps and hose looks like it's not full of fuel? 

Or have you removed the main jet holder and no fuel is coming out of hole in side of bowl?  <--- doing this will tell you for sure if fuel is getting past float valve...  if you have verified fuel is coming out of fuel line to carb.

Yes. and installed a new float it wasn't nowhere close to being adjusted correctly, I adjusted it and problem is solved . Thanks