I have a 2003 WR450 which I bought second hand for cheap, 5th gear was broken and electric start slipping, otherwise no major issues.
I had it for almost 2 years when one day I went through a sharp dip at speed and immediately felt the bike lost power, I rode on for about 150m to where I had to slow down and turn to go over train tracks, when I slowed down and pulled the clutch the bike died and now it refuses to start. I noticed the hot start cable came off from the carb also.
I've cleaned the carb, can see fuel squirting when I turn the throttle, and I have spark. A mechanic told me to take the carb off and give it a kick with my hand over the intake to feel for suction and it has suction so there is compression? I'm going to try and make an adaptor for my compression tester so it fits in the bike spark plug hole to test it, I cannot think of anything else to try.
It does backfire blue flames sometimes after lots of kicking but just wont start.