"modern" 2-cycle engines are very clean buring compared to their simple and older counterparts. What I would classify as a modern 2-cycle is nearly any engine with a self metering oil injection system- these systems lubricate the engine better and with less oil and less smoke than mixing the oil with the gas. Not to mention far less carbon build up. Also because the bearings in these systems are pressure lubricated more power can be made. I think 2-cycle engines are better than 4-cycles in nearly every respect but 4-cycle engines still have advantages over 2 strokers. And with new technology 4-cycle engine are making more power. But the 4-cycle engine weakest point has been with it since the begining and that would be valves- which can leak or become burnt and suffer from many other dissorders.