What’s up with recently rebuilt Hayabusa motor?

Q. I’ve bought a second-hand Busa for good money that’s just had an engine rebuild. The reason I got it really cheap was because it misfires between five and 7000rpm and won’t rev past that.

I’m pretty handy with spanners and electrics so I thought I could sort it out myself. The diagnostics said ‘faulty coils’, but they are fine as is the ECU when swapped with a good one. I’m now stumped.
James Gifford, email
 
A. You say the engine has been rebuilt recently? In which case check the cams have been timed up correctly. If the inlet cam goes in one tooth out, it’s not enough to stop the engine, but the cam position sensor goes doolally and the engine management can’t cope, giving the symptoms you’ve described.