General Tech Choke Connection Rod

[AussieMGB]

Hello; I'm after some advice/general discussion on the twin SU HS4 set up.

Is it common to have only the rear carbi connected to the choke; no connection rod to the front one. Throttle connection is fine of course however, with my limited understanding, I thought it was best to have both carbs choked for the cold starts because of splutting and potential damage to the engine
Admittantly, the choke is only required for about 5 minutes or so however, it's not right in my mind (as are many things in my mind).

As I see it, I have two choices; the easy and the not so easy: Easy Rule 1 - if it works, don't play with working carburettors. Rule 2 - obey rule 1
The more difficult: connect the chokes with a choke connecting rod. Should I go down this path, has anyone had success with the carbs in situ; i'd rather not pull the whole thing apart.
I'm thinking, all I need to do is connect the choke mechanism so they both operate together, how can I get a rod connected between them ( I can get a rod from rimmer Bros for a triumph 1500) . I've got a picture, perhaps this might provide food for some thought.

 

[AussieMGB]

I'm answering myself....Usually, the SU HS4's are connected both throttle and choke, the choke connecting rod has the linkage to move the jet down and then up. With mine, the rear carb choke mechanism doesnt have (need) connecting levers to the bottom of the jet because only the rear is choked. ..seems like a big job... perhaps rule 1 ?

 

[YakkoWarner]

What year car is this? On all the ones I've had (which are early 1970s) the mixture control cable was connected to a shaft that would move the fast idle lobes and pull down the jets on both carbs equally. It looks like your front carb doesn't have a fast idle lobe either, so its very possible it was designed that way in which case I'd leave it as is.

 

[YakkoWarner]

The more I look at this, the less convinced I am it is right. It looks like your front carb actually might have a fast idle lobe, but with the adjustment screw missing. Can you confirm that your front carb does have the movable jet? If so, then it really should be set up to use both for mixture.

If you want to use the connection rod to run the choke on both carbs (which is how all mine have been and most likely correct) you'll also need to get the correct air cleaner bracket for the front carb that has the cable attachment point on it. Unfortunately I don't have any good pictures of mine to show. The closeup of the rear carb makes the mixture cable connection look like its somewhat jury-rigged. Can you provide a closeup of the linkage side of the front carb?

I just got done putting all the together on mine last weekend. Its not really a difficult thing to assemble as long as you have all the peices.

 

[AussieMGB]

The more I look at this, the less convinced I am it is right. It looks like your front carb actually might have a fast idle lobe, but with the adjustment screw missing. Can you confirm that your front carb does have the movable jet? If so, then it really should be set up to use both for mixture.

If you want to use the connection rod to run the choke on both carbs (which is how all mine have been and most likely correct) you'll also need to get the correct air cleaner bracket for the front carb that has the cable attachment point on it. Unfortunately I don't have any good pictures of mine to show. The closeup of the rear carb makes the mixture cable connection look like its somewhat jury-rigged. Can you provide a closeup of the linkage side of the front carb?

I just got done putting all the together on mine last weekend. Its not really a difficult thing to assemble as long as you have all the peices.

Thanks very much, I have checked the cards and yes, both have the movable jetty on the bottom and If I move the choke lever on the front carb, it does move down. To get it all connected would involve removing the carburettors Joining them again with the inclusion of the choke connecting rod and stop attachments. the rod is the 83mm one. This is a job for later(my mechanical experience is limited at the moment. ) Thanks for your valuable advice.

 

[AussieMGB]

What year car is this? On all the ones I've had (which are early 1970s) the mixture control cable was connected to a shaft that would move the fast idle lobes and pull down the jets on both carbs equally. It looks like your front carb doesn't have a fast idle lobe either, so its very possible it was designed that way in which case I'd leave it as is.

It's a 1967 - yes it looked weird to me too - I've checked it all out and the choke leaver on the side moves the jet down (on both carbs independantly). If I can connect them with a connecting rod and install a lever and pin (front and rear) the coke cable will pull the coke lever on the rear and the lever and pin will pull the other up and down also. But, can I install the shaft while the carbs are in place, I don't want to take them off.

 

[AussieMGB]

The more I look at this, the less convinced I am it is right. It looks like your front carb actually might have a fast idle lobe, but with the adjustment screw missing. Can you confirm that your front carb does have the movable jet? If so, then it really should be set up to use both for mixture.

If you want to use the connection rod to run the choke on both carbs (which is how all mine have been and most likely correct) you'll also need to get the correct air cleaner bracket for the front carb that has the cable attachment point on it. Unfortunately I don't have any good pictures of mine to show. The closeup of the rear carb makes the mixture cable connection look like its somewhat jury-rigged. Can you provide a closeup of the linkage side of the front carb?

I just got done putting all the together on mine last weekend. Its not really a difficult thing to assemble as long as you have all the peices.

It's a 1967 - yes it looked weird to me too - I've checked it all out and the choke leaver on the side moves the jet down (on both carbs independantly). If I can connect them with a connecting rod and install a lever and pin (front and rear) the coke cable will pull the coke lever on the rear and the lever and pin will pull the other up and down also. But, can I install the shaft while the carbs are in place, I don't want to take them off.

 

[YakkoWarner]

You can't wiggle the shaft in place while both carbs are bolted down, but its not actually that hard to do. You can leave one carb bolted in, loosen the other and that can get you enough wiggle room to get the shaft in there - depending on how long they have been installed you might need to take one completely off and replace the gaskets if they tear. If you seperate the carb from the heat shield, you would only end having to replace that 1 gasket.

If your fuel hoses are still nice and flexible, you can probably leave them connected but if you will need to disconnect the float vent line if is present (and I would highly recommend replacing the float vent lines if they are missing, because fuel dripping on a hot exhaust can have substantially negative consequences).

It may look intimidating but removing/installing these carbs is (at least to me) a lot easier than doing more traditional style V8 engines. 2 nuts and they pop right off. I'll try this weekend to get some good close up pics of how mine are linked with the factory components.

The factory setup has a lever on the rod itself which is moved by the cable, and then each end of the rod has tabs which fit into the sqaured off openings on the mixture control actuators of the carb itself. Doing it that way endures both move evenly rather than doing it all from one end. That also means both carbs get the same fast idle adjustment as well.

 

[AussieMGB]

You can't wiggle the shaft in place while both carbs are bolted down, but its not actually that hard to do. You can leave one carb bolted in, loosen the other and that can get you enough wiggle room to get the shaft in there - depending on how long they have been installed you might need to take one completely off and replace the gaskets if they tear. If you seperate the carb from the heat shield, you would only end having to replace that 1 gasket.

If your fuel hoses are still nice and flexible, you can probably leave them connected but if you will need to disconnect the float vent line if is present (and I would highly recommend replacing the float vent lines if they are missing, because fuel dripping on a hot exhaust can have substantially negative consequences).

It may look intimidating but removing/installing these carbs is (at least to me) a lot easier than doing more traditional style V8 engines. 2 nuts and they pop right off. I'll try this weekend to get some good close up pics of how mine are linked with the factory components.

The factory setup has a lever on the rod itself which is moved by the cable, and then each end of the rod has tabs which fit into the sqaured off openings on the mixture control actuators of the carb itself. Doing it that way endures both move evenly rather than doing it all from one end. That also means both carbs get the same fast idle adjustment as well.

Some good advice, thanks. I've nearly got all the bits I need (just waiting on the gaskets) I'll try what you suggested and loosen one and see how we go. I measured the space between and I'm thinking I might need to loosen both, but we'll see. The set up will be just as you described, fairly simple, in theory. I've got other things to keep me busy in the meantime- the wiper motor has a short to the casing ( it stopped mid sweep) so I disconnected it and I'm without operational wipers for a while until I can get this motor out ( need to book a chiropractor for after). maybe my wife can get it out, she's bendy...(also a mechanical engineer by trade, great to have around).
I'll search for some advice on wiper motor replacement etc etc. something might come up.
Thanks for your advice.

Peter