YAMAHA ENERGY INDUCTION SYSTEM (Y.E.I.S, "Boostbottle")
Y.E.I.S is a very efficient invention. A small bottle, often called "boostbottle", is installed between the carb and the intake port connected with a branch pipe to get the engine to respond quickly from bottom end without flat spots.
It saves 10-15% in gas consumption and makes the engine wake up at lower rpm.
Like many of Yamahas inventions. When it first came out there were many doubters. Just as they doubted the wisdom of a separate oil pump and the 7th port. Or Torque Induction. But if done properly this does work.
The following diagram shows a typical Y.E.I.S setup. The most common mistake people make is not placing the boost bottle above the cylinder, not getting the size right and using a common bottle for two cylinders and failing to make sure that the bottle drains back without collecting fuel.
Since Carburators can carburate both in and out, when the charge is out of
phase with the engine it creates a double dipping intake charge (passing the
jets twice). This kills the engines ability to make Torq due to this RICH
condition, thus creating the Torq\HP DIP just before the engine starts to
take in the charge and use it all. This Power dip can be seen in both 2 and
4 stroke engines. The ~BOOST~ Bottle will help cure the problem by providing
a storage tank, of the required volume and distance to resonate at this RPM.
It stores the charge that once reversed back through the carb and returned
as a DOUBLE RICH condition.