TR2/3/3A TR3 choke linkage

[NutmegCT]

Not that I'm really into beating a dead horse ...

From my "Practical hints for the maintenance of the Triumph T.R.3" 6th edition (Instruction Book, part no. 501528) manual:

https://www.mgexperience.net/journal/pictures/view/1870

So far it's the only "original" picture I've found. To me it sure looks like the fork of that connecting rod is fully on the engine side of the jet lever on the rear carb, but *around* the jet lever on the front carb.

Tom

 

[pa297pass]

That's great Tom ... I've been saving all these posts as I have to set up the H6's on my TR4 when I put my engine back in.

Since you've become the SU choke expert, I might have to fly you out to Michigan to set mine up!

/bcforum/images/%%GRAEMLIN_URL%%/grin.gif

Matt

 

[NickMorgan]

Excellent picture Tom.
I didn't think to look in the old hand book.
It actually looks to me as though the connecting rod is connected to the engine side of both carburettor levers. And that is how I decided to re-assemble mine as the pins were just the right length for such a set up. It is great to at last have the answer to this quandary.

 

[NutmegCT]

Nick - on second squint - I do believe you're right.

Connecting rod attaches to the jet levers on the engine side of both.

ahhhhhhhhhhh

T.

 

[PeterK]

The parts manual also seems to support the connecting rod around the rear lever. But hard to tell with exploded diagrams. I checked the service manual and it is not specified.

The front is definetely mounted on the engine side of the front choke lever.

I think Nick Morgan's suggestion about the pin length might be the definitive answer. My car came both front and rear of the rod around the levers with a whole bunch of washers to space off the pin before the cotter. It was certainly incorrect.

Why would they make the pin too long? Answer is that they didn't - it's just long enough (as Nick suggested) to hold BOTH rods on the outside of the lever and still pin the retaining cotters.

Now I've got to go out and fix mine!

 

[Geo Hahn]

...Why would they make the pin too long? Answer is that they didn't - it's just long enough (as Nick suggested) to hold BOTH rods on the outside of the lever and still pin the retaining cotters...

So the question then becomes... why would they have a fork in that linkage and not use it?

I still have both my forks straddling the linkage with a spacer on the engine side to take up the pin length.

 

[NickMorgan]

So the question then becomes... why would they have a fork in that linkage and not use it?

A question Tom et al have been batting around for a few days now. It makes no sense that we can see!

 

[PeterK]

The only reason I can 'figger' for the clevis fork is to give a method of adjusting the length of the rod. It would have been much cheaper to build a flat steel folded fork than a heim joint (if they existed back then.)

Dunno why. Good question we have all pondered for a long time and probably will never get answered.

 

[NickMorgan]

I was just chatting this one through with an engineer-friend in the pub this evening. He said that it was probably originally designed to have the lever inside the fork and then this was changed to improve the alignment of the choke cable by putting the fork to the engine side of the lever. He said that they would have kept the fork as this will prevent the pin from twisting when the choke cable is pulled. Otherwise the action of pulling one side of the pin would quickly wear the bottom of the lever.
He also said that the holes in the jet levers are enlarged to allow the fast idle cam to move before the jets lower.
Clever chaps these engineers ...

 

[NutmegCT]

Thanks Nick. And another reason for keeping the fork might be economy; the pins and forked rods were already on the shelves. From what I read about the TR3, Standard Motors wasn't exactly a spendthrift.

By the way, congratulations on getting those sailors and marines out of harm's way!

Tom

 

[NickMorgan]

Tom,
How is your choke now?
Another thing my friend said was that if the inner cable is even only slightly kinked it will make it very difficult to pull. Have you thought about taking the inner cable out and trying to straighten any slight bends in it?
Also, have you checked the alignment of the cable at the open end when the choke is pulled fully out? I would have thought that it is very important that the cable pulls the jet lever in a straight line.
Let me know how you are getting on.
Nick

PS How about buying a new choke cable? If everything moves OK at the carburettor end I would have thought the cable would be the only thing at fault.

 

[NutmegCT]

Nick - There are one or two "bumps" in the cable, but as the cable pulls quite easily when not attached to the linkage, I never thought of removing it. I don't have a clue how to do that - I thought the inner cable was "built in" to the knob assembly and couldn't be pulled out of the sheathing (cable cover). How is that done? If I disconnect the jet lever end and unclamp the sheath, and remove the knob assembly from the instrument panel, is removing the inner cable intuitive?

Interesting issue about that cable alignment. It seems the whole thing is designed "not" in alignment. As the sheath is clamped to that stationary arm, the cable itself pulls slightly upward when retracting that jet lever. I can't see how that could be changed. Ideas?

Thanks.
Tom

 

[NutmegCT]

PS - the choke knob is still quite tight to pull, but at least can be done with only two hands without needing to brace your foot on the door hinge.

Actually works quite well when the lever return springs are disconnected. The problem is much better now after I replaced and greased the o-rings (but I wish I had heard about the vaseline - petroleum jelly - technique before I did the work).

And as you have discovered, when those jets are properly lowered, the engine is soooo much easier to start!

T.