Topic: Best Procedure for Adjusting Mixture Screws (1972 CB750K2)?

[nomadwarmachine]

I am in the process of synching the recently rebuilt carbs on my my stock CB750K2.  I am familiar with the carb balancing procedure using vacuum gauges but I am curious to hear the best way to adjust the mixture screws on this vintage of carbs.   (I checked out the procedure on HondaChopper.com, but the steps become a little garbled and it is difficult to follow).

Has anybody written out, in clear form, the procedure for adjusting the mixture screws for these carbs?  I know that I may have to readjust the synch once this is done, but I want to make sure I am doing it right!  Valves, camchain and timing are all done and there are new plugs.  No weird problems with the bike -- just have not done this in a while and want to make sure I get it right!

Thanks!!

[nancy]

NO mixture screw as such..you have an idle air control stop screw - set from about 3/4 turn to 1.25 turns OUT from full in. Apart from that..mixture as such - is controlled by the slide needle position - moved up or down to make leaner or richer....done with carbs off and apart. That controls higher speed tune. Idle to mid range is not influenced by it. You have removable "jets" that also influence fuel - standard idle jet is a 40 and mid jet 110-120...again with cards apart to mess with these....a 120 will richen th emix and a 105-110 lean it a little. I had 120s in my K2.
Also - the float level needs to be at 26mm. That will influence overall good/bad running. Again - with carbs apart.

So with the carb rack rebuilt and refitted - I think all you can do is adjust the idle stop screw. No gain in changing that unless it is set of spec. That will influence how well the bike maintains idle at normal temperature. It should be left at around the one turn point. 1.25 I think is best. But that is well covered in the manual.

[TwoTired]

Your machine requires and over rich mixture at idle to have good throttle response when the slides are lifted.  It should pick up speed reliably in any gear by twisting the throttle up to 1/2 of remaining throttle travel.

You will want the air screws set to their leanest position while still achieving the above.

Air screw adjustments should not effect vacuum sync balance.  But, you my need to readjust the idle stop to restore proper idle speed.

[AJK]

Without going into an explanation, if its a stock K2 with the stock airbox, if you set them at 7/8ths turn out from the base you should be pretty close if you have a stock setup and have the float levels set to 26mm. You can experiment from there. 7/8ths was the magic mark for my stock K2.