Choke Cable Adjustment

[F1loco]

So, the new carbs are working great, but noticed when I try to operate the choke that:

 

1. More force is needed to pull out than before;

2. The knob doesn't seem to lock or stay out like it did before on its on; and

3. It seems to run "rougher" than before when engaged.

 

Is there some kind of adjustment regarding the tension/lock and is it normal to idle that rough - it's almost like it has a hot cam in it.

 

Thanks,

 

Don

[RogerH]

Hi Don,

the big springs that return the choke to off may be a bit on the heavy side - hence the feel of extra load.

This is not a bad thing as it ensures the choke is off when it should be.

 

The stiffer springs have found that the knob lock position is worn. Just behind the knob there is a brass rod with triangular cuts in. This marries up with a spring loaded blade that locks the position. The brass will eventually wear and the blade slips over it.

See pic below

 

The rougher running is probably because it is running much richer. TRy backing the choke knob off a tad.

 

Roger

 

The top one is quite worn

The lower one is what I remade to work

 

 

Edited September 16, 2017 by RogerH

[F1loco]

Where are the spring returns for the choke located? I think the brass rod looks more like the top pic. Assuming these are still readily available? Is it a PITA to swap out? Thanks.

Don

[RogerH]

Hi Don

 

I have just looked at mine - the return springs are built into the carb/carb cross shaft and are not that strong.

If you lift the cable in the engine bay then it should be quite easy.

 

If it feels stiff/jammed then you have a mechanical problem.

 

The top brass rod is quite worn.

Normally you have to buy the whole cable assembly for mega bucks. If you can make things then it is possible to do so - I did it.

 

Roger

 

Mine are HS6 carb What are yours.?

 

Roger

Edited September 16, 2017 by RogerH

[F1loco]

HS6. I think it must be a non original replacement already. I just loosened everything up on the choke and pulled it out and there are no "V's" - it like a "u" shape 3/4 through the rod and a thin 1mm edge lip around that. It did seem to free up when I reassembled everything so maybe it was more mechanical. My plinth has had it - waiting for package from your side of the pond ...

 

Thanks.

 

Don

[F1loco]

So, I undid the choke cable and noticed it is quite stiff to lift and engage the chokes. I then disconnected the linkages to the choke rod and that freed up the front a little bit, but the rear is still not dropping back down and is quite stiff and binds upon releasing it. I did notice the rear carb linkage bits that the rods go into do not line up like the front carb and seem "torqued" or "crooked" - the fast idle screw doesn't even line up evenly with the choke cam. Do these "new SU" carbs have a tendency to be POS and lack quality control? You would think for $800 they'd be spot on.

[RogerH]

Hi Don,

I've looked at a couple of new SU's here and they all look spot on.

 

Roger

[F1loco]

Well, I little more digging and found where it is binding. The nut on the choke linkages into the carbs when tight seem to bind it. The rear I managed to loosen and tighten it and works pretty good now. The front is being more problematic. Anything more than "hand" tight for some reason is binding. I think it may have to do the washer between the nut and linkage, but haven't been able to find it's sweet spot. It does seem to have play between the washer and shaft it's on, so my guess is when it is tight it is not perfectly centered on the shaft and is rubbing. Now to figure out a solution without hopefully taking the carbs off and disassembly.