Twin Feed or Single Feed Nozzle?

I often get asked "what's the difference between a Single Feed Nozzle and a Twin Feed?" and "why"

Apart from the numerically obvious answer its helpful to consider what's actually going on at the back wheel along with factors like what type of riding you are doing and the design of the swing-arm and sprocket.
In short a Single Feed is easier to fit but a Twin Feed is more efficient!
Here's why...

.... oil applied to the sprocket will move to the periphery of the sprocket due to centrifugal forces – just one side of the sprocket if using a single feed nozzle and both sides of the sprocket if using a twin feed nozzle.
Oil at the edge of the sprocket doesn't stay at the exact edge but will continue to travel up the sides of the teeth.

The teeth taper inward to reach a rounded/chamfered point so the oil follows this line - if you were to "freeze frame" this you would see a shallow linear pool of oil stretching from the sprocket outer face over the edge and onto the inner face of the tooth.
If there was no chain then this oil would gather at the tip of the tooth, form a droplet and fly off.

However, once the oil reaches this point it is at the mesh of the chain rollers with the sprocket teeth. Any oil on the inner face of the tooth will be displaced by the action of the chain roller when the 2 mesh together. This literally squashes the oil - in the manner of an oil pump – out of both sides of the sprocket tooth and onto the o rings/x rings on both sides of the chain rollers.

Obviously with a Single Feed Nozzle there is more oil on the feed side of the sprocket tooth so it is necessary to compensate for this by slightly increasing the flow rate to ensure that the non feed side gets enough oil.

If you use a Twin Feed Nozzle its possible to increase the efficiency ( and reduce oil usage) because you can direct only the required amount of oil to the rollers without having to compensate for as much wastage.