Topic: Tuning up a 77 hondamatic, need a couple specs

[Wykydtron]

Hey, tuning up a 77 CB750A for a coworker, I dont have a manual for it, Im very familair with the 550's and Ive read plenty on the 750's but I need a couple specs.

I need the exhuast and intake tappet adjustment specs.  I also need the factory mixture screw setting for the carbs(how many turns from lightly bottomed). 

Is gap/dwell for the points the same as on the 550's?  When I adjust the cam chain, is it the same as a 550? On the 550 you rotate the crank until the TDC for 1-4 shows up, then continue to rotate until the stud that the spring for the advancer mechanism weight attaches to is just past the timing mark, then adjust the chain since the slack will be at the back of the engine.  Same thing?  I know the 750 cam chain adjuster is different and tends need a little coaxing for it to adjust.   Thanks!

[JohnG]

hi
I will look up the valve specs for you when I get to my shop.  The points would be  .012-.016".  The cam chain procedure you describe is one that is in 750 literature and should work fine.

            john

[JohnG]

Made it out to the workshop through the 3" of fresh snow we got last night in New England  (there go any ideas of a first ride on the 750 today....)

OK...referring to Honda Motorcycle Service Specifications for all 1959-1980 US Models

      plugs:  D8EA     .024-.028
      point gap           .012-.016
      dwell angle         190  +/- 5 degrees
     
      advance
           F   10 degrees BTDC
           max advance   23.5 to 26.5    at 2500 RPM

       intake valve clearance   .002"             exhaust   .003"     (same as other cb750s...)

It seems to treat 1976 and 1977 as identical. Let me know if you need any other specs...

       john
       1976 CB750F

[JohnG]

for 76-7  it says to use 1 1/4 turns from closed.  78 seems to have a different carb and all different settings including 1 1/8 turn from closed.

Tight spots? Yep... the 5 speeds would be the same. Only the gear box is really different on the one you are working on. I just set my valves and the the ones right by the frame members were... no fun.

Shifting?  I remember Cycle magazine reviewing the bike and the cover reading  "Shift or Go Blind"

[eldar]

One thing that has been suggested by hondaman is to go slightly larger on the valve adjustments. by .001 on each  so .003 and .004.  This is supposed to help with valve wear as the parts expand from heat and thus allow the fuel and exhaust to move better.

The screw on the 77 will meter fuel so turning them out will make the bike richer and in will make it leaner. I would say to start at 1.5 turns out and check things from there.

I also read a thing on the hondamatic. while there is no shifting fun, it was supposed to be great for touring and the rag also noted that while you were in traffic, you did not have to worry about shifting and so could concentrate more on the cagers.

[eldar]

that is possible. I could not start this weekend using the starter and it had low voltage. I could however kick it but I dont know if the autos had kick. for some reason I dont think they did but I could be wrong!

[eldar]

On the left side? OK yeah, that is kinda queer. well what the hell!