i have new brake controls and when it sits for a few days it leaks out.would it be the rubber boot that you see or something inside.they are after market from v-twin

 

I don't have a clue what year or model bike you are referring to.
I don't know of a "rubber boot" on the stock master cylinder. (maybe a pic would help)

V-Twin mfg. is well known for their poor quality, Chinese "knock off" products.

 

Where is it leaking from? The gasket between the cover and body of the master cylinder is a dynamic seal. When the bike is sitting there isn't any pressure or fluid against it that would cause a leak. Without knowing what exactly is leaking or what exactly was replaced, it's tough to say. Did you reuse any copper washers or replace with new? Did you follow torque values?