Topic: Carb sync question

[6adan]

70 CB750
    Had to replace throttle cable so now I need to sync carbs
 1st.
Dose the airbox need to be on or off?
  2nd
I have two manuals but they are not very clear to me on this.One says to use the adjusters on the top of the carb and the other says to use the slide stop screws,so I am not sure witch way to go.Any help would be great. Thanks Dannie

[keiths]

I'm sure that someone with more experiance than me can tell you the proper way, but this worked for me. If the slide stop screws are the ones that adjust the linkage, I made that adjustment first, making sure when I turned the throttle all 4 sliders started moving at the same time. Then with the air box on, I used the top screws with the lock nuts to make the final adjustments.
Hope this helps.
Keith

[Johnie]

Just did my 1970 CB750KO this past summer for the first time.  And with the help of this board I might add.  Keep in mind the sync is the very last thing you do.  First you have to have good plugs, valves adjusted, timing set, good points, etc.  Then you are ready to sync.  I used the Morgan Carbtune.  Get the bike warm and then set the idle at 3,000 RPM.  Then use the cable adjustment screws on the top of the carbs to sync at that RPM.  Once that is done you are ready to sync the low idle screws which are the big screws on the sides of each carb.  Do not get frustrated as it will take some time.  I did it and then had to redo the slow idle later.  Mine idles nice at 1400.  Be sure to turn a nice strong fan on the engine during this process so you do not overheat the engine.  This is all done with the air box in place.  I can even do the sync with the gas tank in place.  I just use a piece of wood to hold the back of the tank up high enough so I can get at the top adjusters.  I can also get my fingers in there for the slow idle screws, but if you have fat fingers that may be a problem for you.  Good luck with it.