I've had several 140's and 240's, and now have a '91 740 with a B230. As part of my "acceptance inspection" I was changing the plug wires, rotor, and cap. I could not believe how much crap was on the inside of the cap! It looked like it was on the south side of a northbound dog with the trots, if you know what I mean. I thought there must be a major seal leak back there (can't see squat with this setup), but it appears to be the result of an amazing design that leaves a large 'hole' in the forward facing edge of the cap. I assume this is for some kind of ventilation? Does anybody have a clue on this and should I expect to be changing or cleaning my rotor cap every 100 miles Thanks!