Topic: Carburetor - Choke Rod adjustment

[Toby84]

Hi,

I’m assembling my carburetors, and ran into an issue while adjusting the choke rods between each carburetor. I can’t seem to have no 3+4 to close the choke properly AND open completely. It is either a perfect closed position or a complete open. If I can’t have both, which is most important? Does the choke work good enough if it is not 100% closed? Will the bike run properly if the choke is not 100% open when turned off?

I hope the attached pictures will clarify. It’s not much that is missing, but it’s there as you can see.

[ekpent]

One picture is the choke flap and the other picture is the throttle valve which all need close to the same gap for a bench synch. What bike are the carbs from your working on ?

[Toby84]

I believe that they are k2 carbs, they are not a match with my k7 (cb750 If it wasn’t clear).

Yes, and what I mean to show with the pictures is that the one with the choke flap shows how the flap doesn’t close perfectly. And the picture with the throttle valve shows how the choke flap doesn’t disappear completely, if you look closely you can see it in the top (I don’t know why my pictures appear upside down, sorry about that).

So my problem is that I can’t adjust the flap (by turning the rod that connects the choke on all carbs) to be perfectly closed AND completely gone when raised, I have to choose one of them (or I’m
Doing something wrong). And in that case - which is most important? To have the flap completely closed while chocking or completely out of the way while not choking?

[pjlogue]

I found the same problem with my '76 CB750K 40+ years ago.  I am not sure how much of a problem this poses for starting/riding but the cause of the not full open/not full closed is due to the slop in the ganged linkage from carb one to four.  My solution was to get a piece of brass tubing that was the same ID as the stamped in post on each of the choke arms.  I then drilled out each eyelet a bit so it matched the OD of the brass tube.  This arrangement took the slack out of the ganged linkage so that when carb #1 choke started to close (or open) , so did #4. 

As I said, I do not know how much of a difference this makes for every day starting/running.  If I remember correctly it seemed to help on a real cold start.  (this memory is 40+ years old)  I think the only difference it would make on warm running is when you were going WOT and I never ride that way unless it is for very short bursts.

An added note; I also seem to remember readjusting the linkages as being a REAL PITA!  LOL.

-P.

[Bodi]

Personally I set them so they are fully open with choke off. Being a crack open at full choke won't make much difference, and I've never had starting problems. I did an experiment setting them all to close 100% and could not tell any difference in cold (40F or so) starting. Who starts a 70s classic motorcycle when it's colder?
I vote for minimal obstruction at WOT.

[Toby84]

Thank you for your thoughts.
I’ll adjust for minimal obstruction at WOT.

Let’s see if there will be any choke issues. This is how it looks by now with this adjustment when the choke is activated: