Read work file with a variable length record

I have a work file record I am trying to read. It is a variable length record archive of a database file over several years, so it cannot be loaded back in to Adabas easily. It contains 4 fixed fields: field1, field2, field3, field4 and 2 mu fields (field 5 p9(1:50) and field6 a4(1:50)). I’m having difficulty reading the record properly. I mostly get invalid data for numeric input field. There are no delimiters in the record. I can see a 1 byte mu-count fields in the dump of the file for field5 and field6