Bought this bike, a 2003 WR450, about 4 months ago, and it's been working great all this time. Last time out though, it failed to start after I'd shut it off while waiting for others to make it up a hill. We ended up towing it back to the truck. To summarize: - it was working fine prior to it failing to start. - starter would only spin, not engage (may be a red herring because it sometimes acts up when the bike is hot) - could not get it to coast-start, but it fired a bit, and backfired a few times while trying. - left it overnight to cool, but still would not start the next day, although the starter was working again (until the battery went dead). - tried towing it with the truck and was able to get it started if I held the throttle open about 1/4 - 1/3, but it would die immediately as soon as I let the throttle close and still backfired when trying to start. - the bike got very hot in the couple of minutes I had it running. - cleaned the carb, but still no change in starting / running abilities. The bike has had the free mods and has the latest version of the starter gears. If anyone has any suggestions as to what the problem may be, or what to check next, that would be appreciated.