Mick

From what I can find the mvvs 91 is listed as 91 GFS-R ABC R/C. That means it's a ringed front intake side exhaust ABC engine. If this is the case it should be run in like a ringed engine, slow and rich at first to allow for ring seating. Then thermal cycle it.

It's not unusual to use ABC technology on ringed engines anymore even though many would ask; WHY? the brass or the chrome. Actually chromeeing iron liners wasn't unusual a long time ago in hopes the liner would be more durable or to recover a worn liner

Denis