E-Type carb/choke question

[a8hex]

I believe that the carb setup on my XK150 (it's got a 4.2 lump and straight port head) is similar to the arrangement on the E-Type. It has a manual choke on the centre carb.
So a quick question for the E-Type aficionados out there. Does the choke have a return spring?
Mine doesn't and the choke seems to be failing to return properly and even when pulled from under the bonnet to fully close it, it seems to creep back open while driving.
Should there be a spring pulling the damn thing forward?

[1954etype]

The only springs are under the jets. The choke is controlled by connecting the carbs to the dash lever via a piano wire. There is also a ratchet on the choke lever to hold it in desired position. BTW, all 3 carbs are choked, not just the central one.

[427James]

Agree entirely with the above post. My father is building a set for a S1.5 conversion back to S1 spec. Will PM his email if you want photos of anything or to chat it through?

[a8hex]

Thanks guys.
I'm not sure why CKL only put the choke on the middle card when they did my conversion.
I guess I need to work out why my choke is tending to stick open and why it also want to creep open.
The "quick fix" is probably just to adjust the cable to when it is pushed home it definitely shuts.
At least I know now I'm not missing a spring.
Cheers

[jith]

a8hex said:

Thanks guys.
I'm not sure why CKL only put the choke on the middle card when they did my conversion.
I guess I need to work out why my choke is tending to stick open and why it also want to creep open.
The "quick fix" is probably just to adjust the cable to when it is pushed home it definitely shuts.
At least I know now I'm not missing a spring.
Cheers

I've not been on here for a while a8 because, quite frankly I'm having a helluva bad time right now, but I'll help you out with this.

A common conversion to the 3 carb setup is to use a Mk X manifold which of course, has an auto choke system for cold start. To go to manual choke you have to reverse-engineer the carbs to properly enrich the mixture. Having the choke on only the centre carb means you have to use more choke to get the engine to fire initially and keep it on longer. This means the two centre cylinders are running far too rich and you will get accelerated bore wash wear on these two cylinders.

The manual choke should operate on all 3 carbs with a linkage that pulls down the main jet diaphragm adjuster, i.e. the lever on the bottom of the carb that contains the mixture adjustment screw. At the same time there is a cam assembly that lifts the throttles slightly to give you fast idle. If you don't have all these parts on your carbs the car will never run properly when cold, and you will have the problems you are having.

The good news is that all of these parts are available from SU. Check out this diagram of the HD8 carb:- http://sucarb.co.uk/carbspec/carburettor/spares/id...

You will need parts 32-25 plus the choke linkage that joins them; times 3 of course! I would phone SU and tell them what you are doing with the carbs and they will supply everything you need. The parts won't break the bank and will get your XK purring the way it should.

J

[a8hex]

Thanks Jith,
Starting the car isn't a problem. My problems are when it gets stuck in traffic for a while and things warm up. It then goes all lumpy. I'm then finding that although I've pushed the choke cable hard home from the dash it hasn't closed up properly at the business end. If I to the gynaecologist trick and pull the cable forwards at the carb end then it seems to creep back open again a little bit.
At low revs she's still kicking like a mule even when warm but as the revs build it goes a bit fluffy.
Obviously I need to spend more time driving her away from traffic ;-)

[Flatinfourth]

a8hex said:

Thanks Jith,
Starting the car isn't a problem. My problems are when it gets stuck in traffic for a while and things warm up. It then goes all lumpy. I'm then finding that although I've pushed the choke cable hard home from the dash it hasn't closed up properly at the business end. If I to the gynaecologist trick and pull the cable forwards at the carb end then it seems to creep back open again a little bit.
At low revs she's still kicking like a mule even when warm but as the revs build it goes a bit fluffy.
Obviously I need to spend more time driving her away from traffic ;-)

Firstly, the chaps at CKL are the most helpful, friendly bunch to deal with, any questions should start there. Also they may have good reason for the simplified choke arrangement, is the car a circuit biased build for instance? The choke is sprung by the jet for the additional fuel, and the cable linkage is sprung for the fast idle side. Normally the lever is held against the spring to start the car, then eased back to the fast idle positions once running

[mph]

OP why haven't you asked CKL as they carried out the conversion ?

[a8hex]

mph said:

OP why haven't you asked CKL as they carried out the conversion ?

I haven't had the chance yet. Odd working hours. I need to have a chat with them about the rev counter conversion as well as the rev counter's died and its no longer the original mechanical driven one, it takes an impulse feed from the coil.
Its not been a problem in the past, but it now sticking.
The engine has always started OK with the choke. I'd just never realised before that my arrangement was a bit odd, that was all. The engine was somewhat track focused :-)
I've adjusted the cable and oiled all the links in to the carb and its still sticking.
It might just need a new choke cable, there also seems to be a lot of play in the cable in that I can move the carb linkage best part of half an inch without the knob end moving.