When I bought the bike some 2 weeks ago it would run just fine. Then some days later, I noticedd occasional misfiring of one cylinder when idling. Recently I took the bike out for a trip, and it ran on one cilinder most of the time. When you rev it up it suddenly starts to fire both cylinders. And now it stops at idle speed (it reverts to single cylinder mode then ;-)), and it is very difficult to start it. The bike has been standing still for a long period of time I guess. I replaced the battery, and checked the (original) sparkplugs for wear. I added a cleaniing additive with the fuel - but that didn't solve anything. Does anybody have a clue? Currently there is about 9000 miles on the tacho.