I have a '01 YZ426. I absolutely love the power but there is something very bad about this bike. I'm about to trade it in on a 2-stroke. I had no problems in warm weather at all. Now that it's cold, the bike will only start on a new plug. And you guys know what a pain it is to change plugs. It will run all day and you can re-start it as long as the bike stays warm but as soon as it cools off ya gotta change the plug. Then it'll start on the first kick. I have a WB E-series exhaust, BK mod. I've tried both the stock jetting and a 148 pilot with a 165 main. Any help would be greatly appreciated. I love every other aspect of this bike. But it caused me to miss a moto at my last race. If I can't get it fixed I WILL be mixing gas again.