after being completely whupped by a 2cylinder motorcycle,I have to share the out come with anyone that it might help now or in the future.If you kept up with the story,it started with rear cylinder misfire under load.I rebuilt carbs,plugs, compression check,set valves to specs, changed ignitor module, checked pulse generator,finally replaced rear carb.42 years as auto truck mechanic,this one beat me UP! after each repair I thought i won.NOPE.until today.Ive had this happen many times through the years on autos. never thought it could happen on a 2cylinder dual exhaust motor bike.left exhaust pipe sooted up after 7 years of storage it ran well until every thing broke lose,and then the nightmare began. I hope this helps someone GB