I took my bike to an independent mechanic to get dual disc brakes installed on my dyna.

the problem is now the front brakes feel very spongy and weaker than when I had one disc brake.

needless to say I will never go back to this motorcycle shop again.

they also charged 900 dollars labor to replace my fork legs that were already preassembled included with the disc brake, caliper, and master cylinder I provided

 

Probably left air in the system. I assume they updated the original master to the bigger one for dual calipers?

 

I did yes I gave it to them to install

 

Bleed them. Again.

 

Bleed them and report back.

 

Bleed from the caliper up.

 

Tell us the whole story, have you brought the bike back, explained the problem, and given them the chance to make it right?

 

".....they also charged 900 dollars labor to replace my fork legs that were already preassembled included with the disc brake, caliper, and master cylinder I provided....."

If they charged $900 for the work allegedly done. there's no way that they could make it right unless they give a partial refund.

 

There is no reason for you to quote my post, direct your questions to the op...

 

Wow, $900 seems pretty steep.
Take the bike back and make them bleed the brakes, then ask for a detailed list of what was done to warrant a $900 bill.