Thanks David Dymaxion. I spun it up to 1000rpm with my drill. Slight vibration but the motor didn't jump off the bench
I tried undoing the flywheel, turning it 180 deg and bolting it on again. Exactly the same 0.13mm bump so I guess the flywheel itself is good but the hub is off centre.
I was wondering if this could be due to the weight of the flywheel pulling the spline down? Maybe it'll straighten up when the pressure plate is applied.
Seemed to be two bands where there was some harmonic and the loose tools on the bench started to rattle. Otherwise ok.
I got a fright at how much power it takes to spin that flywheel + motor! My drill is 650w and it took around 25 seconds to get to max. I'm guessing it'll use at least 4kw to spin the whole lot up to 2500 rpm in 5 seconds or so, as with normal driving.