Re: Newb with a '78 CB750A question

Posted by kandrtech on Feb 09, 2013; 8:20pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Newb-with-a-78-CB750A-question-tp4036035p4036389.html

In all due respect, my Honda literature indicates that the auto carbs have 24mm venturis, while the K/F carbs have 28mm venturis.

According the parts fiche:

77/78 K carb holders are 16211-405-000, and 16212-xxx-xxx (same), 16213, 16214
77/78 F carb holders are 16211-410-000, and 16212, 16213, 16214
77/78 A carb holders are 16211-393-020, and 16212, 16213, 16214

77/78 F/K air box to carb holders are 17253-405-000
77/78 A air box to carb holders are 17253-393-770

Upgrading the auto bike carbs to the 28mm carbs net a nice boost in HP.  The problem with that upgrade is the lack of 77/78 carb holders.  Going with the older round tops is the better choice, as you can then also buy the round top carb holders.  The down side is that the accelerator pump wasn't provided until 77.