...
The most common cause of 400 errors from Solr is the length of the text field that Aspire tries to feed. In Solr 5.4.x, the default "text" field type has changed and in Solr 5.4.x it - it now uses "strings" which don't allow big strings to get indexed.
To fix it modify the its type of it to be "text_general" (in the managed-schema.xml file on Solr) and that ; this should resolve your problemsthis error.
...
...