Kawasaki KIPSKawasaki's KIPS exhaust valve system has gone through a steady refinement of design. Kawasaki uses a different system to suit the needs of the different model bikes. The earliest KIPS design used two drum shaped valves to control the flow of the sub exhaust ports. Opening the ports gave the exhaust port more time-area. The main exhaust port was relatively small with modest timing and duration. A rack and pinion set up controlled the drum valves, opening them at about 6,000 rpm. Kawasaki uses the rack and pinion design in all their KIPS systems except the 1998 and later KX80-125cc models. The 1992 KX125 and KDX used the next generation KIPS which featured a center wedge valve with two side drum valves engaged to a rack-and-gear actuating system. This system was very complicated with all its moving parts. The top and bottom racks had to be synchronized through the left drum valve, which has two drive gears molded in it. The drum valves are made of aluminum. When the drum valve becomes carbon seized, the steel teeth on the rack shear off the aluminum teeth on the drum valve, rendering the drum valve inoperable. Check the condition on the gear teeth every time you do a top-end service, because if one gear fails the whole system runs out of sync.
On the late model 80-125cc KXs, the KIPS is relatively simple relying on a wedge valve and flapper. This system is self-scraping so it requires little maintenance. In the first year of operation (199
the KIPS system was plagued with failures like the pin breaking on the flapper, the valve receding into the cylinder and contacting the piston, and over-extension of the valve causing cock and jam. In 1999 Kawasaki changed the wedge valve and flapper design for more rigidity and that solved all the reliability problems.
However, the drum valves eventually wear at the drive channels for the center wedge valve, and the sloppy fit between the wedge and drum valves prevents the center valve from fully opening. That is why these bikes get noticeably slower as they get older. There is no preventative cure or aftermarket part. You just need to replace the drum valves when the drive channels wear out.
1993 was the first year for the KIPS system used through present day models. The system uses a single wedge and flapper valve for the main exhaust port and two drum shaped valves for the sub exhaust ports. The valves are all linked together with two racks and pinions on the right drum valve and a steel gear on the upper rack linking the wedge valve. A left-hand-thread nut retains the gear to the rod that actuates the wedge valve. Check the nut periodically, if the nut loosens, the wedge valves become inoperable.
