I bought a 2006 WR450 a few months back.
Took it for a ride today on the road. I accelerated with moderate/heavy throttle. About 3/4 throttle full load the bike basically fell on its face. I did it a few more times with the same result. It also backfires after a hard take off.
It rides great with normal riding (fast but not under heavy load, blipping the throttle every now and then)
The bike has been uncorked (not by me, the previous owner). I've recently got it plated, and put about 200 road miles on it just tooling around.
The problem is more noticeable while on the road.
-I changed the oil 150 miles ago
-I replaced the filter 3 days ago. (no off road riding since filter change)
- I have no clue if its been re-jetted
-still has stock silencer on it, not sure if its been modified