17-03-14, 07:54 PM
The yics system was designed to cause a swirl in the incoming mixture improving combustion at mid to low revs, improving fuel economy and mid range power, I know in the late 70s when yamaha added yics to the xj650 it did improve the mid range power as they were a bit gutless at low revs, there was an article in the early 80s which did a rolling road comparison by blanking off the yics chamber and it did make a small difference, the reason why it won't work properly on the fazer is the pipes are too small and n the wrong place, they need to angle towards the port, the science behind the linking of inlets is it can improve fuel economy as you can in some cases use less throttle, in the real world it will be difficult to confirm or deny, I know when I used the slightly smaller bore t pieces the bike did vibrate more at 3k revs and when I replaced the t pieces with bigger internal bores the vibration did virtually disappear. Ideally the linking of the inlets should be with a 10mm internal bore pipe not 5 or 5.5mm pipe.