Does anyone know if a 1974 Honda CR250M came from the factory with fork emulators? I am in the process of changing the seals on my Vintage MX bike and noticed something "new to me" in the forks. A web search found they are emulators. My intentions were to braze one or two of the inner tube holes closed to slow down the dampening, but that has already been done. I'm wondering just how much work has been done to these forks. Regardless, new seals and oil will help a bunch. They both leaked, and only had about 2 ounces of oil in them. "War is an ugly thing, but not the ugliest of things; the decayed and degraded state of moral and patriotic feeling which thinks nothing is worth a war, is worse." --- John Stuart Mill:
Do your "emulators" sit under the fork springs and have an adjustment bolt sticking up on top My 1973 CR250M had plain old damper rods in the forks. An emulator is a device which emulates, or behaves like, the flexible shim stack in a cartridge fork. Race Tech's simple Gold Valve Emulator is an adjustable spring-loaded round plate which relieves excess pressure on rapid compression. The basic problem with damper rods is that they have fixed orifice holes in the side of the tube, and a certain weight of oil can only pass through a hole of a particular size at a certain speed in order to achieve the desired rebound damping. Riders who want more rebound damping will use a heavier weight oil and when the fork stroking speed doubles, the damping force quadruples. At some speed the hole damper rod is just too small to allow the passage of significant amounts of oil, and the fork becomes very harsh, it can't compress fast enough because the oil won't flow through the hole. The Gold Valve Emulator blows off the excess pressure through the top of the damper rod to the upper fork chamber. My old 1968 Yamaha 250 Single Enduro had a sort of foot valve on the damper rod. Shock absorbers have foot valves under the piston to relieve excess pressure on compression and they close again on rebound to slow the flow of oil. The damper rod in a fork has the piston on top, the damper rod is upside down compared to a normal shock absorber, so a foot valve on a damper rod would be on top and could be thought of as an "emulator"... My Yamaha's foot valve had thin wave washers that acted as springs to control the foot valve motion. The wave washers broke after a few thousand miles and Yamaha couldn't sell them to me separately, they wanted to sell me a whole new damper rod assembly. Yamaha's racing engineer showed me the simple 1969 damper rod with holes and no moving parts and told me that it was "improved"...
