Throttle Cable

[Tournesol]

Good evening all,

I've tried to find previous post on this but couldn't find any relating to my issue.

The throttle cable on my 1968 +2 (UK drive) has gone loose from the pedal. On inspection it appears the spring at the other end of the cable (by the carburetors) is dead and the small piece of brass (sorry don't know the name....) holding the gainter in place is shattered.

When I pull the cable (the play is about 6-7cm) just before it goes through the hole by the brake and clutch fluid bottles I can hear something hanging behind the engine bay partition. Is that the throttle return spring there?

Here is the queries I have (bare in mind you are talking to a complete novice when it comes to mechanics):

1) Is the cable secured somehow behind the engine bay partition on its way to the pedal? If so how do you access this? Do you need to take the brake and clutch reservoir out? If not how do you guide the cable all the way down to the pedal bar link?

2) Is the cable secured on the handle bar linked to the pedal by anything? on my car it looks like it just sits in the grove on the bar link

3) Do I need to get a full throttle cable or can I just get the spring and gainter attachment for the carburetors end?

I am pretty sure you will have questions to answer my queries, so shoot and I'll try to give all the needed info.

Thank you for your help!

Tournesol

[marklowe]

Hi,
I think a photograph of your carburettor linkage would assist in understanding what set up you have and what has gone wrong,
You are correct in that the pedal end of the cable just sits in a notch on the link, and is held in place by cable tension / weight of the pedal.

Mark

[Tournesol]

Good evening All,

I took some pictures tonight so might be better to understand what I meant in my poor attempt to explaining with words.

Do I need a full length cable or is it possible to replace just the broken parts and what are they called?

Thank you for your help!

Tournesol

[mbell]

The cable end connects to the bracket on the airbox not the throttle lever. The outer casing goes in to the throttle lever.

So the cable comes from the pedal box, the outer goes into the throttle lever. The inner continues down to air box and fits into a slot on the bracket.

I'd be tempted to replace that cable personally.

[john.p.clegg]

especially as its got a frayed strand..

John

[tonyr27]

For now I would cut off the fraid strands, hook the nipple back on to the air box bracket and slot outer cable onto linkage on the webers. That should get you going, while you wait for a new cable from Sue Miller or one of the other suppliers.

Good luck.

TonyR

[billwill]

We are talking about Weber/Dellorto carburettors are we not, not Strombergs?

~~~~~~~~~~~~~

This is the pedal end (from our incomplete Wiki)


On a two-seater like my S3, there is a fixed triangilar bracket on the engine side of the airbox, with a key-hole shaped notch on the bottom edge. The 'pear' shaped nipple on the end of the throttle cable fits in the keyhole notch forming a fixed endpoint for the inner cable. Contrary to normal expectations, the inner stays in a fixed location and the outer cable slides along the inner to open the throttle.

At the carb end, the outer cable fits into the sideways barrel shaped nipple which has a notch in its side for the inner cable. This then fits in the U shaped end of the throttle lever on the Weber/Dellorto carburettors; You juggle these in a bit at a time, so that the inner cable is on the closed end of the U part of the lever (as a safety precaution in case the Outer Cable ever managed to pop out of the barrel nipple). Normally the tension of the spring prevents it popping out and the bottom end of the spring can be made to restrict the nipple at the end of the inner from dropping out of the keyhole slot.

The spring is number 102 on the following diagram and the throttle bracket is number 42


The outer fitted in the throttle lever can be seen in this photo from the gallery:


The inner cable in its keyhole slot can be seen in this photo from the gallery, though this seems to have an unusual dumbell-shaped nipple (or it may be an outercable cap than has slid down to rest on the 'pear' shaped nipple). The end of the spring can be seen; though it can often be arranged so that the spring prevents the nipple going sideways out of the slot by having a spring with a long-ish Hook on the bottom and having the main body of the spring further out from the bracket and hence 'outside' the inner cable. This may require drilling a new hole in the bracket for the bottom end of the spring in a location nearer to the airbox than the slot for the throttle inner.





The outer throttle cable in its barrel nipple can be seen in this photo from the gallery, and this also shows the upper end of the return spring.




~~~~~~~~~~~~


If you know exactly what to do and if the outer cable and its adjusters are OK you can do as I do, go to a bicycle shop to buy a bike brake cable and some screw fixed nipples; but otherwise buy a ready made complete cable from one of the usual suppliers.

[pharriso]

Excellent post Bill... I was looking for pictures of the cable arrangement at the Carb end but do not have any good pictures... the arrangement is not obvious.

[SF69Elan]

Tournesol - thanks for asking this question, and thanks to everyone who replied with all the great info and pics. I'm planning to switch my linkage from one of the overhead bracket systems to this "lighter" option when I install a factory style airbox.

Rich

[JJDraper]

As an aside to this discussion, be aware that the throttle arm can be shorter than Weber's standard one.

IIRC the shorter one is Lotus' way of making the throttle response 'snappy', Talking of which, check that the return spring is still in one piece, as they can wear through or snap, as per pic.

Jeremy

[john.p.clegg]

...and sometimes the holes in the replacement arms can be too close to the fitting and too small to fit the spring..

John

[Tournesol]

Good evening,

First thank you all for your comments.

I've ordered a new cable from Sue Miller (very helpful Lady) which arrived in the post the following day. I'll try to fix it later in the week if I got the time or over the week end. Not sure I totally understand how the whole accelerator is working but fingers crossed all will make sense when I am faced to it. Then the car is going to Miles Wilkins for a new chassis and suspensions before going for a new MOT.

Enjoy the roads!

Tournesol

[davidc]

Doh!

Spent ages last night trying to figure this out after putting carbs back on.

Couldn't figure why throttle needs to go downwards but cable comes from above!

Seems an odd way but it works.

Fantastic forum helps again.

[pharriso]

Yes it's interesting... try working out how the hood (bonnet) release works, that's a good one too!

[mbell]

As an aside to this discussion, be aware that the throttle arm can be shorter than Weber's standard one.

Does any one know the measurements for the shortened throttle lever?

I find the throttle pedal travel is too long on my car. So thinking about modifying one of the longer replacement parts to many a original one.