Nope. Mount it up and bleed it at the line on the master cylinder, then reattach the line and bleed further down. 
I just did one. Simple. 

-craig

On Jun 25, 2013, at 6:44 AM, Robert Clemmer <n51219@COMCAST.NET> wrote:

> I'm about to replace the master cylinder on my 91.  Is it necessary to bench
> bleed the master cylinder before installing?  Bentley don't mention yea or
> na.
> 
> 
> 
> 
> 
> Bob Clemmer