Can someone help me understand the engineering behind the accelerator pump? I don't understand why you would want to jet to exacting specifications if all you are going to do is dump an un-managed amount of raw fuel into the intake with every twist of the throttle. Seems like it would just screw things up, or seriously hamper trying to achieve good jetting. I know about the BK mod. I'm just wondering why it leaves the factory with up to a 3 second squirt. On some tracks you don't even hold the throttle open for over 3 seconds, so every time you open the throttle its always squirting. What effect does this have on jetting? Assuming you have done the BK mod, does make your bike too lean? Does yamaha account for the long squirt in the Jetting specs? Its just seems way to unscientific.