After a thinking I was over the hump of the learning curve a new hump popped up. I had been all set going out several weekends and putting in a few flights each time (I'm not an early riser so I get to the field just before the Socker Kids and only get in a couple flights before they start their games). Anyway, a couple weeks before the fall contest everything goes wrong with a very bad vibration - rough running that would not settle down. Well I miss the contest and a few weeks later I decide to do some tests, fire up just as it was and it shakes like mad. I changed the prop to one that worked early on and poof problem goes away. I fly for several weeks and think well maybe for the King Orange meet we will be ready. Then three weeks ago it starts again, this time changing the prop made no difference, talking to Eric Clutton he suggested that maybe the prop washer got pushed a little to close to the case and once the engine warmed up it started rubbing which increased the heat which etc. etc. etc.. Anyone have this happen and what kind of clearance do we need?