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?