Xk140, or 150 carbs and start-up

I am working on a 1956 XK 140 DHC for the widow of a friend. I am looking forward to starting the engine today after a cartb rebuild. I have an XK140 manual, ut the carbs they show are not what’s on this car. I think these are 150 dual carbs. Can someone refer me to the initial settings for the air bypass and enrichment screws please? Thanks, Mike Moore ! Here is a photo. 2a5f8bc2509937a1-IMG_0876|375x500

I usually just set then to 3 turns out from fully seated, then adjust as necessary, after balancing and refinement of jet height.

What about the richness screw?

If you are talking about the screw that adjusts the jet height, I forget the actual measurement from the jet bridge, but setting it about a millimeter below the jet bridge will get ya in the ballpark, then use standard techniques to refine, once installed and the engine is started.

Thanks Paul-My bigest concern is just getting it started and running on gasoline (instead of starting fluid) once it;s warned up a bit I can adjust the richness and idle speed . It is mysterious-not sure what car these carbs came from. maybe an early 150. The plugs were very very sooty and the choke adjustment was way way rich and the start carb was disconnected. I don’t know how it went with us to SLO years ago, but it did.

These are HD carbs rather than H . I think you are right , this type fitted to 150

Mike the starting carb IS the choke. What setting are you referring to?

Phil, there is an “enrichment” setting which sets the height of the jet w/r to the bridge. This car was set way rich and I do not think the thermal system is working-yet. Plugs are very very sooty although it has not run in ten years. Phil, I am going to test the coil next time I’m over because with12 v on the Primary side new cable and new plugs, I get no spark. I plan on removing the distributor and put new points and condenser in it. What is the easiest way to remove the distributor? It looks to be impossible through the top although I suppose I could walk it back toward the firewall. Thanks, Mike Moore

Understood. Paul has answered your questions on initial settings. I was confused when you referred to the choke setting. Once you slacken the distributor securing plate and pull the distributor out its just a case of jiggling it about until you find the best route. Not all engine compartments are the same so my RHD experience is probably not relevant

I am unable to see the bridge on this car and I was hoping somewhere there would be instructions LIKE “tighten the enrichment screw until it touches the lever then rotate it 1-1/2 turns in” or something like that. And a clue as to whether or not I’m better off jacking the 140 up and removing it from under the car or not. Thanks Phil for your help! What part of England do you live in?

Take the dashpots and pistons out, and the jet tube, relative to the bridge, is easily seen.

I’m in the southeast of England. With a bright light, dash pots off, you can see the jets. As per Paul’s suggestion. The various books suggest anywhere between 2&3 turns down from where the jet is flush with the top of the sleeve. Easier to visualise than describe once you get into it.

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I should have thought of that! Thanks, Mike


I want to thank everyone for their help I have received to date. Today it ran-sort of! I have not been back on this car for a while except sporadically. To review, I am trying to get this car running so it can be driven safely and reliably water 8 years of not running. The brakes are complete although still satisfactory but I have set that aside until I can at least move the car under its own power, To date, I have replaced all the wire core ignition wire. soldering the brass discs on, with boots on both ends. I have had the distributor rebuilt and "modified for modern fuel’. It has new plugs, points and condenser, cap, and rotor. The carbs have been rebuilt with new kits,
Today, I jacked the egine around until I was at 5 degrees BTDC on a compression stroked (air pressure on my thumb plus a seconf=d check with compression guage. I have double checked the firing order and rotation by ringing out each wire.
I was able to get it to fire and run briefly on ether today.

I disconnected the fuel rail and ran some gasoline out which is at least 2 years old and was pretty yellow,

Checked the fuel tank and it was empty, We added 5 gallons of 91 octane gasoline , started it again on ether but can’t get it to run on gasoline.

My attention now is to the thermal choke which I had left disconnected. Karen (owner) tells me there is a switch under the dash for the “choke” but it doesn’t work very well and they had to let it run for 5 minutes at least when they used to drive (8 years ago). I determined the switch (which had a guard type cover) was a cut in the ground wire. In other words, the ground side of the “choke” was through the switch, the other side to the low voltage side of the ignition coil.

My plan now is to disconnect the flex line to the fuel rail and drain enough gasoline out to get clean gasoline out to make sure clean gasoline is going to carbs, then reconnect it.

I also confirmed a blue white spark at the plug. I had set the timing statically by rotating the distributor slightly until my doorbell buzzer continuity tool rang, I also confirmed the rotor was pointing to #6 cylinder.

I know nothing about the thermal choke. Is there a reference someone can recommend?

Thanks ,

Michael Moore
XK-140 (whose cam cover says C)

The XK120 Service Manual covers it.

The mixture on the thermal carb can be adjusted by the nut F on the top.
The normal Otter thermal switch connected to ground when cold, with the other side connected to the coil SW side, not CB, so your bypass manual switch to ground should be fine. Many of us do the same thing.


Thanks so much.

Mike Moore



Michael, after you worked on the carbs, did you turn the jet adjusting screws all the way up (clockwise) and then back them off by 2.5 turns? This is what’s recommended in the Service Manual to assure there’s a rich enough mixture to run the engine.

After you get the engine started and warmed up, then you go through the procedure to fine tune the jet adjusting screws to optimize the mixture.

Thanks Mike
Since I don’t remember, that is at the top of my list. Thanks so ,much for the tip!
Michael Moore

Rob and others,

Today I visited the car

with a list of (1,) ensuring I was getting clean gasoline delivered to both float chambers , (2) ensuring the thermo carb was working correctly (3.) checking settings of the air bypass and richness level of both carbs and (4) starting the engine again.

First discovery was that no fuel at all was coming into the banjo fitting for the front carb, I removed the fuel rail and found clean fuel filters in each float bowl. Putting each rail end banjo in its own glass contained. We pumped clean gasoline only into the rear. The front banjo was totally blocked, Not a drip, I used a piece of braided steel cable and cleared it. Nothing came out and I still don’t know how it was blocked. Checked it and both banjos now had fuel. I then checked out the wiring on the thermo to the coil and its bypass swiitch and it was all good.I set the air bypasses out 3 turns and the jets approx ,040 inches below the bridge.

We tried to start it using the thermo and it never fired, I sprayed the rear carb with ether and it fired and seemed to be on the way to an idle but it repeatedly died. I had Karen turn the thermo on, sprayed some ether again, it spit, the thermo sneezed spouted gasoline and I momentarily had an EPIC fire as the ether soaked towel I had on the fender ignited, Fire was quickly out. The car had seemed to run quite well while it ran,Karen the owner was ecstatic to hear her car run and that was worth the effort,

So, I want to adjust ti a smooth reliable idle obviously, but to have the engine warmed uo, I have to start it and everything including the thermo asks for a warmed uo engine.

I was concerned about the geysers of gasoline I had this morning out ot the two holes in top of the thermo, I understand that is caused by backfiring with gasoline piled up in the intake manifold, Is that in the thermo or in the actual intake manifold? Should I drain them first? How?

Thanks for all the assistance .
Mike Moore

There should be an anti-backfire valve in the connection of the starting pipe to the intake manifold. It is probably stuck open with old gummy fuel residue.
I don’t know what it looks like on a 140, but here it is for 120.

When you get a backfire, the fuel in the starting carb and pipe will blow out the top unless this valve is closed.

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