I don't think there is a size limit for young riders. I checked D.M.V. through their website and there was nothing there about size limits. This is what it said.
Young Riders
Teens 16 and 17 years old can obtain a motorcycle license by following this process:
1. Apply for a learner's permit (also known as an instructional permit) for a conventional license.
2. Attend and complete a driver education course at school.
3. Apply for a 12-month motorcycle learner's permit.
4. Study the Motorcycle Manual and the Rules of the Road.
5. Enroll in the 20-hour Illinois Department of Transportation (IDOT) Motorcycle Rider Course. This course is free. Find out more by calling IDOT's Motorcycle Safety Project at (800) 892-9607 or (800) 642-9589.
6. Hold your learner's permit for at least three months. During this time, you are allowed to ride the motorcycle only in daylight hours while supervised by a qualified motorcyclist.
7. Pass the motorcycle road test at any local Secretary of State driver services office.
A new motorcycle license costs $10.
