The Honda CBR 600 starter motor is stronger and fits EXCEPT that the mounting bracket has to be fitted from the later model (2005+). It can be noted by the fact that the original mounting bolts are used but the starter is longer! Loonyberg fitted one and it’s really easy! The starter can fit the original bracket, but you need to drill fresh holes and a little filing, super easy to do! And due to the windings in the Yamaha R6 (1999), the starter from the Yamaha spins far faster and enables his big 650 to start every time.