If it has a C&H Synchro Spark, could be the ignition is not retarting as it should be. Nay be the reason for both problems. You should call the guys at C&H and have a talk with them. They should be able to halp if it is an ignition problem. Easy poeple to deal with, and really helpful.
You can find the number here: http://www.ch-ignitions.com/