I have a older K&B 61 that has a tendency to heat up. Doesn't seem to make any difference on how rich it is (other then it runs horible when it is too rich). It has a tendency to quit when I put it on the ground (gently from the stand) But then times it will run OK and I can fly for 10-12 minutes no problem. Next time I start it, it may do all those bad things. Had 2 or 3 instructors look at it and had no idea other then it was a K&B. Thanks for looking