13B parts:

Front iron housing- 23 lbs

Center iron housing- 28 lbs (with dipstick and filler tube)

Rear iron housing- 27 lbs

Each rotor housing- 13 lbs

Each rotor with seals- 10 lbs 9 oz

Water pump housing- 3 lb 2 oz

Water pump- 5 lbs 9oz

Eccentric shaft- 14 lbs  (estimate a single rotor would be 5.5 lbs less)

A bare 13B engine is known to weigh 190 lbs.  The items in red above would be removed from this base weight.  The total of these items is rounded to 66 lbs.  That brings the base engine weight to 124 lbs.  As a rough estimate, let’s say the other necessary accessories for a total installed weight will be half as much for a single rotor.  We often claim 330 lbs FWF for a 13B.  If the basic engine weighs 190 lbs, then the “other” stuff weighs 140 lbs.  If  I add half of this (70 lbs), to the estimated weight of the single rotor engine, that brings the total to 194 lbs.  This is not too far from the full installed weight of a 912S, which is probably around the 175 lb mark.  So far, it’s sounding promising, even with no extraordinary weight saving measures.  Affordable aluminum end housing would sure be nice though.