TR4/4A Throttle Linkage

[Popeye]

Hi all,

I am near completion on my TR4A assembly, crossing off the last items on the “to-do list”. My throttle linkage is a bit sticky. If I push the accelerator pedal, it does not (always) return.

I have not yet debugged the problem. (I replaced the bushings and three springs with new during assembly.) I plan to take apart one joint at a time and see where the “sticky bit” is; hopefully I can isolate it to one joint, not several.

However: what is the correct procedure for installing the adjustable links? Parts 14 and 145077, parts #10 and 13 in attached image. They thread into a mating piece, and a lockwasher plus nut are threaded on. Should the threaded part be screwed tightly to the mating part, followed by a tight nut? Or should the threaded part only be tightened a little, allowing space between the moving surfaces and the nut used as a locknut?

Also, I assume the ball joints in the links should be lubricated? (With graphite??)

(SU HS6 carbs)

thanks!

 

[charleyf]

Hi all,

I am near completion on my TR4A assembly, crossing off the last items on the “to-do list”. My throttle linkage is a bit sticky. If I push the accelerator pedal, it does not (always) return.

I have not yet debugged the problem. (I replaced the bushings and three springs with new during assembly.) I plan to take apart one joint at a time and see where the “sticky bit” is; hopefully I can isolate it to one joint, not several.

However: what is the correct procedure for installing the adjustable links? Parts 14 and 145077, parts #10 and 13 in attached image. They thread into a mating piece, and a lockwasher plus nut are threaded on. Should the threaded part be screwed tightly to the mating part, followed by a tight nut? Or should the threaded part only be tightened a little, allowing space between the moving surfaces and the nut used as a locknut?

Also, I assume the ball joints in the links should be lubricated? (With graphite??)

(SU HS6 carbs)

thanks!
View attachment 90464

I use the HS6 carbs and this linkage on 2 TR4s and a TR3A. The answer to your question IMHO is that the threaded bolts or studs that you refer have a lock washer and should be tight not loose.
Where I have found problems has been with bolt 16 and nut 19. I have replaced lock washer 18 and replaced it with a flat washer. Then have used a lock nut. Just make sure this step bolt functions and is not loose or wobbling. And the fulcrum sitting on the step bolt is not wobbling.
Lubrication of the ball joints should be grease.
If your pedal is not returning to full off, my first place to look is at the two springs shown in the picture and then the spring on the accelerator shaft.
To me any loose joints in this system cause slow response when the pedal is depressed and also prevent a full off when pedal is released.
Charley

 

[Popeye]

Thanks Charley. I’ll check 16/18/19 - I believe I reused original hardware… it might be out of round, etc.!

 

[charleyf]

Thanks Charley. I’ll check 16/18/19 - I believe I reused original hardware… it might be out of round, etc.!

The fulcrum and ball joints wear as well. The ball joint can be tightened if need be also.
Charley

 

[Popeye]

And the verdict, as Charley predicted, is the fulcrum pivot. Stiff. I’ve ordered new, assuming the original part is no longer “round” - and not terribly expensive.

Thanks!

Fingers crossed…

 

[charleyf]

And the verdict, as Charley predicted, is the fulcrum pivot. Stiff. I’ve ordered new, assuming the original part is no longer “round” - and not terribly expensive.

Thanks!

Fingers crossed…

My advice would be to replace fulcrum and step bolt/ pivot. Not just one part.
Charley