Here is a Copy out of the AMM (Aircraft Maintenance Manual ):
Start the Engine Procedure (Normal Start)
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When the engine is at 25% N2 or the maximum motoring speed, move the start lever to the IDLE position.
If the engine speed is less than 25% N2, you can move the start lever forward to the IDLE position when the engine is at its maximum motoring speed.
NOTE:
The maximum motoring speed is defined as the speed when the rate of increase in N2 is less than 1% during a 5 seconds time period. The minimum maximum motoring speed is 20% N2.
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HIH
