Hi I'm restoring a 74 dt 125a I've replaced replaced the fuel tap as I didn't have 1 with 1 from yambits which has a 6mm outlet but the carb has an 8mm inlet so I put a 6mm to 8mm reducer in the problem i have is when I have the pipe all connected up fuel does not flow but does if I don't connect the pipe to the carb. 
I'm after ideas as to why this would be?

Cheers 

John

My guess is you're using clear fuel line which they didn't use originally because it interacts with the polar vortices and blocks the flow of fuel*.  Replace it with solid black fuel line.

*Not really.  It's just an illusion that you can't see with black fuel line.  So ignore it or replace with black fuel hose.

Yep just replace & forget it. It'll be flowing at a speed to keep up with the fuel use out of the bowl. You'll be looking at it with the bowl full I'm guessing. Either that or the float isn't dropping, but ignore that comment, does it run ok?.
We've all done the clear hose trick at some stage.
In saying that I'm about to see if the fuel is flowing to the pumper carb on my chainsaw looking at a clear hose I fitted. So no hope for me haha.