I bought a RMZ-250 the first year they came out. I raced it in 04 in Alaska and did alot of trials too, then I went to Iraq and my buddy rode it for 05 in Hawaii, I rode it for half of 06 in Hawaii until I bought my CRf-450. I changed the oil frequently and rode the heck out of it. I sucked in some water once too in a river incident in Alaska and rode it 10 miles popping and sputtering back to the truck. It never blew, I never checked a valve, I didn't even know what those were. It never blew up. My 450 I raced from 06 until 09 when I went back to a 2T, and same thing minus the water. I rode it hard and never had an issue. I don't think the problem is that 4T's blow up more, the problem is when they do go it costs alot. All I ever did was change the oil at the proper intervals and kept the air filter clean. You are not going to get a 125 top end to last a season if you ride it at peak rpm all the time and hold it too long at maximum rpm, but it will be easier and a heck of alot cheaper to fix.
