I'll start off by saying I am a newbie to this, but it seems to me that changing the oil shouldn't cause this much trouble! I bought a 2000 YZ426 used, and once I got past the learning phase as to how to start it, it was a one kick bike. After getting some hours on it, I decided to change the oil. I started it to warm it up (one kick) changed it, put in a new air filter (old one fell apart when I cleaned it) changed the oil, and couldn't get it started. I went out riding the next day and it took 20 minutes before I finally got it going. The next weekend, I changed out the spark plug and it started easier, but after about 15 kicks. A friend who had a YZ400 said that if you put too much oil in it creates too much pressure and is hard to start. So tonight I changed the oil again. Started on the 4th kick, changed the oil, put 1.4 quarts in (less then recommended in the manual) and guess what, won't start. I'm using Yamalube 20w40. Any suggestions as to what to look for? Like I said, I am new to this so...one thought I had was that I may have used too much filter oil on the new air filter. Is it possible that some of it got sucked into the carb and is gumming it up now? It is acting like it's flooded. I can't go two weekends without riding! I'll never make it through the next week of work!!! Any suggestions are GREATLY appreciated.