We present the results of an Automatic Speech Recognition system developed to support linguistic documentation efforts. The test case is the zahrar sproche language, a Southern Bavarian variety spoken in the language island of Sauris/Zahre in Italy. We collected a dataset of 9,000 words and approximately 80 minutes of speech. The goal is to reduce the transcription workload of field linguists. The method used is a deep learning approach based on the language-specific tuning of a generic pre-trained representation model, XLS-R. The transcription quality of the experiments on the collected dataset is promising. We test the model’s performance on some fieldwork historical recordings, report the results, and evaluate them qualitatively. Finally, we indicate possibilities for improvement in this challenging task.