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I have a recently acquired 1978 CB400T II Hawk that I need some carb advice on. The bike seems very original and complete but when I got it there were obvious signs someone had been working on it. The carbs and entire airbox assembly were loose with all the screws MIA but otherwise the bike was intact. To sort things out I’ve removed the airbox and carbs from the bike and what seemed like an easy carb cleaning has now turned into an exercise in confusion. I admit I’m a noob with these later Honda twins this being the first one I’ve toyed with, but I am familiar with the earlier twins. With that said, I had no idea there were so many different variations of carbs on these bikes!

My issue is this. The carbs that were with this bike are VB22G’s with the accelerator pump. These are not the carbs this bike had originally as the G’s were for an ‘82 CM450 I believe. While perhaps these would work on the ‘78 400T the main problem is the primary nozzle in one carb is hopelessly stuck. And not only stuck, it’s also clogged with a broken off EZ out (don’t ask, just suffice to say it’s Homer award worthy:oops:). I do not believe it is repairable and am now looking at having to replace the carb.

The question is would it be better to try and replace this one carb in a non-original setup or use my misfortune to now try and source the correct carbs for this bike which would be VB21A’s? Would a single useable VB22g be harder to source than a matched rebuildable set of VB21’s? The 21’s seem simpler than the 22’s with the accelerator pump but is there a marked performance difference? Thanks for any help or suggestions.
 

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Imho I would go with the stock VB21As with stock jets. As you said there are so many variations that another set VB22Gs could have jets that can cause all kinds of problems till you get them sorted out.

Bill
 

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The VB21's have the larger venturi, 32mm, which will produce the most power. I'm running 22's on the road bike, originals were 21's, and it's not quite as quick as is was. Other than that the 22's are working just fine.
 
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