Front master Cylinder Probs

Well just rebuilt the front master cylinder on and old FL it is an old V-Twin master with 3/4" bore, now when trying to bleed the brakes the master cylinder is building pressure in itself and pumping it right back in the reservoir. There are 2 small holes in the bottom of the reservoir one is a pressure and the other is a return. when i am pumping the brakes slowly to remove the air in the master on the bench it works fine, when all the bubbles go away in start pumping for bleeding and the pressure starts and enough pressure that it shots out the top (cover off) and can't get any pressure to the line for some reason. I have double check the re-build set up and it looks just fine. Any Ideas? Could the maser Cylinder be junk to not pressurize the line just itself? The lid for the master has a small vent hole and when the lid is on it pumps brake fluid when pumping for bleeding. Already rebuilt the Caliper and New line. Got the bike with leaking fluid from both, they are both about 20 years old. Caliper is a Jaybrake 4 piston.

Is the bike an Evo or Shovel?? Is this 3/4" bore rebuild kit the same as the one you got??
http://www.jpcycles.com/product/2400390..
Here's instructions for that kit
http://img.jpcycles.com/staticwebfiles/instructions/pdf/2400390.pdf
Hope that helps a bit

Thanks Lucifer, it is a Shovel and he decided to not do it, he is going to sell it here in Europe. Rebuilt both and just did not work. I have rebuilt a lot in the past, some you can rebuild some you can't.

Duals can be tricky,probably is a bubble...Strapping the brake lever into the hand grip and leave it over night,then do the screwdriver thing can bring a bubble up.
Mighty Vac is a good tool for the box, comes in real handy for brakes (and lots of other uses), it's one of those tools you don't need often,but when you need one you're glad you have it.