I hear ya...I think the bike could use some help getting into the power quicker, especially at the track. After riding both the 03 YZ450 and CRF450 I wanted my WR450 to have some of that low-end instant hit. I'm getting tired of those guys getting the jump out of the corners, particularly when there is a rhythm section right out of a hairpin. And, I figure with electric start, if stalling increases out on the trail, I can easily restart. I'll take the chance if it means more throttle response.
I checked with Steahly with the same question about flywheel weight and they didn't know offhand how much it weighed, but said that it was heavy and machining down the flywheel is the best bet. As much as 6 to 8 ounces would be a good start (of course it depends on where you remove the material). I asked if their kits for the YZ450 are meant to mimic the WR flywheel and they said no, that the WR flywheel was still heavier. Next Tuesday I'm pulling the flywheel and having it machined.