Actually it's not a press fit it's an interference fit , the two are not the same but most people think they are, the difference is in the clearance between the two parts , on a press fit the two parts are pressed together with a hydraulic press , a crankshaft pin is an example of a press fit, an interference fit requires the shaft or flywheel in this case to be frozen and the bearing or ring gear in this case to be heated, when the two are put together they cannot be separated after a few seconds.
On some Yamaha flywheels the ring gear is also staked onto the hub, this has to be ground down to remove the ring gear, I mainly see this on 701's .
The cylinder sleeves are also an example of an interference fit , the cylinder is heated and the frozen sleeve is dropped into it..
Most press fits can also be achieved by heating say a bearing and quickly dropping it onto a shaft, this is commonly used on motorcycle -ATV engines where the cases are heated and a bearing is dropped into the cases.
