Jaguar XK120 Throttle Stop

There have been a few conversations recently about the Throttle Stop fitted to XK120 cars new from the factory. They were put on to restrict the Accelerator from being fully depressed, depressed (Full Throttle) until the car had been run in for the first 500 miles or so. These were supposed to be then removed by the servicing dealer and the customer then drove away happy.
Well, after a considerable amount of investigation, I was able to get a couple of images of an original Jaguar XK120 Throttle Stop and recreate one. This is what you see in the image attached. This is interesting to me because all the cars that left the factory had one fitted, where are they now? I am sure this will generate some comments. Thank you.!

Jaguar XK120 Throttle Stop #A|446x500

Where did it fit?

Sorry this seems to have loaded incorrectly! The Image A should be first and Image B second!!

any chance of getting picture of the original part you copied from? terry

Page 21 of the XK120 Handbook describes the throttle stop. Original owners must have been frustrated to learn this would be bolted to the accelerator pedal during the initial break-in period.

I guess that’s what that hole is for.

Here is what the original XK120 Throttle Stop looked like.

G’day Terry,

I have posted a couple of pictures of the Throttle Stop on Jag-Lovers Forums. Here are the same attached.
Best regards,


Same hole in my 120 pedal, and not in my similar Mark V pedal, so I am inclined to agree.
And with a red BEES bolt!

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The Bolt is a 1/4 inch BSF and the small hole next to it is for the Lock Wire and Lead Seal.

That’s my story and I’m sticking to it!!!

Here is what the Throttle Stop may have looked like with the Lock Wire and a Lead Seal. Can always be removed if you don’t like it!

A little more to the story of the throttle restrictor.

It is described in Service Bulletin 66 from April 1950 for XK120.
Perhaps it was not on earlier cars.
It is also described in Service Bulletin 69 from July 1950 for Mark V.
You know what lead-foot pedal-to-the-metal drivers those Mark V owners were.

Pretty much the same wording in both, to prevent excessive speed during early life, secured to the pedal by a setscrew, locking wire and lead seal, to be removed at the first service after 750 miles, notification to all distributors and dealers, and that they should inform all casual traders.

I believe the XK120 owners should have an authentic reproduction Throttle Stop in the trunk of their car to go along with the Tool Bag, MRO Box, etc.

Makes you wonder if that 1100 mile alloy car in California still has it; did it ever get it’s 750 mile service?

There has been very little response on the subject of the Throttle Stop. Is this because very few people have ever seen one, never heard of one or…? I am not suggesting an “Authentic” XK120 should have this part fitted to the Accelerator Pedal, but I for one, would certainly like to have it for reference with the rest of my XK Kit, in the Trunk or with the car. Similar to the Jaguar “MRO” Boxes with Spares for the cars from the factory, most of which never got to the Owners but were removed at the Dealers and went into “Spare Parts Stock” at the dealerships.


In reality no 120 owner would have the stop as the mechanics would have removed it during a service and chucked it.


In fact a few of the factory Throttle Stops have survived, but only a few.
As a Jaguar enthusiast, I would like to have seen cars with the Throttle Stop displayed at a concours. Just my personal opinion! Some owners display a number of hard to find items like the “MRO” Kit containing spares for owners who may need to do their own maintenance. The “MRO” kits are very rare and people are asking silly prices for them.
Back to the Throttle Stop, I am sure some owners would like to have a authentic reproduction part including the very rare 1/4” BEES BSF Bolt, Lockwire and Lead Seal.


I completely see your point and I had no idea they existed before this discussion. I never stop learning about these cars.


kinda tongue in cheek…but IF…for Concours the car is to be as it left the factory, with a throttle stop in place, and some USA cars would not have headlights and many parts would be covered in cosmoline for the sea voyage, early cars would have a engine oil dipstick of the early type.

Hello Nick
I believe that a car leaving the factory had to have all the parts to pass a roadworthy test. If it was shipped with RHD lights that was OK because the car was in the UK and would meet UK requirements. After shipping, when it reached the USA, the Jaguar (USA) facility would have the responsibility of having the Lights changed ( to LHD configuration) before it went on to the dealer and then the Customer.
Cosmoline or Ensis Fluid was applying to the Chrome parts to protect them from the salt on the long journey over, to the USA or Australia or…
As far as the Throttle Stop goes, if a car is shown on the green, it would be nice to have some of the bits and pieces associated with the car from day 1.

Karl Robertson