The bike and all its standard ancillary parts are insured under the motor vehicle policy. So, if you were claiming for two engines and three frames, they'd just say no. If the vehicle is under repair and the motor was out, it'd still be considered a complete vehicle. A loss adjuster would probably be sent round to ascertain the details, so if your motor was nicked and not the rest of the bike, they'd probably take that into account when calculating a payout.