MF-65

It sounds like the carb mixture may be too rich. You could try adjusting the mixture and seeing how it works. It may be that you have to remove the carb and give it a thorough clean and soak. I had a similar erratic running problem with my 65. I was always having to readjust the carb to get it running OK, and then it would only do so for a short period of time. After dismantling the carb and doing a carb cleaning, it has run extremely well. These carbs are very easy to take apart, just make sure you don't lose the needle when you take it apart (it will fall out when you take the halves apart). While there are relatively expensive carb soaking solutions available, I did mine over a period of several days in laquer thinner, and used compressed air to blow out all the small holes several times over these few days (remove the rubber o-ring and cork gaskets from the adjustment needles before the soak). The only other thing you will need is a new gasket when you put the halves of the carb back together.

Pat