Hi,
The excerpt is create in bp-blogs.php on line 284 (RC1) calling function bp_create_excerpt in bp-core.php line 807. bp_create_excerpt takes a limit parameter which defaults to 55 characters. It doesn’t look like you can easily adjust this without hacking the core, although I am no expert so you might be able to also hack an action together that will adjust the excerpt.
Thanks mspecht…I tried editing the bp-core.php to see if it would shorten the blog post in the Site Wide Activity, but the site wide feed doesn’t seem to use bp_create_excerpt. My Site Wide Feed shows about 250 characters (not 55), although it does seem to be showing exactly 55 words. I’d like it to be more like 10-15 words…Any other ideas?
ok it seems the comments around bp_create_extract are wrong it does 55 words it defines a word based on spaces. I tried changing the default $excerpt_length from 55 to 10 and my site wide activity only had 10 words.
dont touch the code!
Hacking the code is the last thing that you’ve to do with bp 
(I’m from mobile now, so i cant see it now) I’m sure that posts excerpts or forums ones have a filter, use them!
after you’ve found the filter, use it writing a function to cut text, as i’ve done for forums and add that as filter.
Where do I change the excerpt_length
Here’s one option:
I used advance excerpt Plugin https://wordpress.org/extend/plugins/advanced-excerpt/
Activate and set the excerpt word number.
and place the <?php the_advanced_excerpt(); ?> in the index.php
This works for me.
I am trying this plug too http://www.dailyblogtips.com/homepage-excerpts-wordpress-plugin/
