I found an S&S Owner's manual online:
http://www.sscycle.com/files/7113/7033/9290/106-3756.pdfPage 5 has the service intervals and for the timing belt is inspect every 10,000 mile (16,000 km) and replace at 30,000 miles (48,000 km).
I'm not sure if Morgan follow these recommendations or have more frequent inspection/replacement......