Topic: CB650 VB44A carbs (pics added)

[Scott S]

 I'm cleaning up a set of Keihin VB44A carbs from an '81 CB650 and have a few questions:

 1) Do I HAVE to run the vacuum petcock cut off? Can't I just plug the hole in the throat of that carb nd run a manual petcock?

 2) Can I elminate the accelerator pump? This model only has the accelerator pump on the #2 carb. What would happen if I changed the float bowl on that carb and omitted it?

 I have a few more questions and some pics, but that's it for now...

[starsnbars89]

I can personally say that I bypassed the vacuum cutoff and it worked fine. Don't know about the accelerator pump. I always enjoyed having mine.

[Scott S]

 I'm looking at the rebuild info here:

http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revD.pdf

 ...and it appears that my acc. pump assembly isn't installed correctlt. The stuff around the choke linkage doesn't look like his instructions. Plus, the diaphragm is bad. I'll keep it if I can figure out how to fix it.

[starsnbars89]

I know that you can get a new diaphragm kit for it. Other than that, can't help you without seeing it. Look at a part schematic and narrow down what is missing/improperly installed.

Something like this: http://www.cmsnl.com/honda-cb650-1981-usa_model7224/partslist/

[tomkimberly]

Everyone I know has already by passed the vac petcock. Fix the acc pump, it will greatly help you for cold starts, twist the throttle two - three times before you hit the start switch.

Tom

[Scott S]

 I'm trying to get a clear shot of my acc. pump rod and the tang. The manual says there should be 0.4-.06mm between the tang and rod. Adjustment is made by bending the tang.
 I have WAY more that that.....I'd have to really mangle the tang to get it correct.

 I can't save pics from the .pdf file that I posted before...
( http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revD.pdf )
   ....but on page 27 he shows a view of the choke braket and mechanism. Mine is different. I didn't de-rack the carbs and don't see any evidence that they've been apart. I also don't see a way to move the tang assembly around.

 I hard, old diaphragm wouldn't collapse enough to created a huge gap between the rod and tang, would it?
 

[Scott S]

 Here are a couple of pics of the accelrator pump rod and it's tang. If I'm reading my manual correctly, that gap is supposed to be 0.4-.06mm. As you can see, it's WAY more than that. I'm beginning to suspect that someone replaced the diaphragm with the wrong part.
 I have one on order and I'll see how it fits.



 This is where the choke cable attaches. It looks like it's in a different position than what is shown on the .PDF rebuild file I posted earlier in the thread. See page 27 (I don't know how to save the pics from that type of file or I'd post one for comparison). Does this look correct for these carbs? It seems to work fine by hand.


 I still need two pilot screws. Other than that, the carbs are clean and ready to go. Look closely in the first pic at carb #2 and you can see the acc. rod and tang, too.

[starsnbars89]

You may be on to something with the wrong rod idea. You said the diaphragm was bad anyway so ordering a new one and finding out is a good idea. If it fixes it, it's fixed! If it doesn't, you know something is missing/assembled wrong! Process of elimination.

[Jbosma]

I also have 1981 CB650 with the same carbs (I think). Am I supposed to have an air cut off valve? My clymer manual shows it having one but I don’t even see where you could put one on. Thoughts?