Sloper refers to the forward leaning cylinders. Early Honda twins were all actually slopers, with exception of the 450 engine. In 1969 the CD175 went to a vertical twin, so those 175's before the transition are called "slopers".Very nice! Im new so no advice on sourcing parts, but will follow to check your progress. What is the background on the term Slopper? We just got a 61 C92 that looks similar.