I thought I made the first reply here, but it musta not posted...
I have had a ported 7900 for 8 or so years. Problems: leaky oil system...fixed with new improved parts
weak starter assembly--fixed with new improved parts.
Weak buffer springs....no fix..some just break a bit before their time
Filter too small, clogs easily, fixed with improved plastic filter cover, or the magnum cover and bigger filter.
Other than that and a coil or other problem that makes the saw hard to start when hot, the saw has been great. I also have two Makita 6401's that I got from Home Depot when they were selling off their rental units. (Happens often, watch or call to get a great saw for ~$200.) Both in fine shape, just needing the above fixes. For about $200, get the 7900 jug and you have a very fast saw that only needs a muffler mod to whip a similar modded 460 or 372, with ease. I also have a muffler modded 5100S. Also sometimes hard to start when warm, otherwise has never had a single problem. Nor did the ported one (by Ed heard, the first ever ported 5100) till it, along with many other saws, was stolen.