I just recently acquired a 1968 Mercury BP 1250.of course after I purchased it I found out there is virtually nothing available for it.long story short sometimes the motor runs like a sewing machine and sometimes it doesn't.the number 3 cylinder appears to have compression sometimes and sometimes it doesn't.a quick check with the borescope shows perfect cylinder walls,good spark,and compression that seems to come and go on that cylinder.Two Strokes are somewhat of a mystery to me.what next,start looking for a more modern engine or fix this one?