08-29-2014, 02:38 PM
I was a mechanic in a Honda, Yamaha, BMW, BSA and Greeves dealer when the CB750 came out. The first ones had cable splitters, the one throttle cable from the twist grip pulled the 4 separate carb cables out of this splitter. Carb syncing was tedious and lasted for a couple of high speed blasts. All the fours had vacuum ports to plug gauges into. All of the big four quickly changed to common throttle shafts which helped a lot. There is a couple of aspects to throttle synching. First, the idle mixture had to be adjusted so that all cylinders fired at idle. If the air mixture was off, the throttle adjustment could be right and the idle would still be terrible. At an idle everything is so close to being closed and off it is hard to get perfection. Also those bikes had two ignition systems. All fours fire 1,2,4, 3. 1 and 4 had a set of points and coil; 2 and 3 had a set of points and coil. Timing could easily be off between those two sets of cylinders. Also valve lash is an important component of a stable idle. I’ve always been a proponent of setting valve lash to minimum specs, seems to make sense, less room to bang components and maximizing valve lift. However a stable idle on all those old fours was best achieved with the middle of the lash specification or at the upper end of it. This was particularly true of the Kawasaki 900s/1000s. I have a great appreciation of My CB1100 as I stare at my dusty sync gauges hanging above my workbench. Hale, My Ural even has FI. The chance of your CB1100 being out of sync much is slim or none unless some busy fingers have been in there. After a while, I got to care less what my Kawasaki’s idle sounded like as long as all the throttle slides reached the top at the same time and under load it ran fine on all four cylinders. A heat gun is a good tool to see if all the TBs are working ok. When you first start it up, get the heat gun out and check each head pipe at the same distance from the head. They should be in the same ballpark.