Unusual SBs are not my thing barge, but we have had the Model 31, and in particular the 201 engine, come up here before. Most of the discussion was in relation to the Wipac Magister ignition system the 201 originally used. See this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=37014#Post37014

Your engine is presumably a later one since it does not seem to have a Magister fitted. I believe the 201 was a specific engine made by or for Scott Bonnar, and was one of the mildly oddball adventures the company undertook. You might find some interesting background in this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=46183&Searchpage=1&Main=8230&Words=%22201+engine%22&Search=true#Post46183