Students with dyslexia often suffer from the lack of academic self-worth and frustration that can even lead to learned helplessness. However, few studies have investigated the impact of incorporating users' motivational factors into user modeling to enhance the learning experience for students with dyslexia. In this paper we attempt to develop a conceptual motivation model for people with dyslexia in their use of assistive learning tools. To this end, we carry out a small-scale empirical study in real-world learning scenarios. Then we conduct individual interviews to gain first-hand data about the key factors and features affecting learning experience. Using coding and thematic analysis methods we discuss main themes regarding motivational factors and their interrelationships identified. Based on these findings, we create a conceptual motivation model tailored towards students with dyslexia, which will help enhance learning experience and improve learning efficiency.