Lotus Elan

Throttle linkage what do members recommend

PostPost by: Concrete-crusher » Sun May 28, 2017 4:03 pm

Hi I have very early twin Webers dcoe 40 (serial number 67 on one of them)

They have just had a professional rebuild but I can't get the idle constant , in fact its starting to stck around 3000rpm . I have tried adding a return spring but it's not helping.

I see Tony Thompson does a kit , has anybody used this and does it fit below the flat bonnet ?

What other return linkages fit ? I have a few issues with popping but this one should be simple to fix first , I hope.

Thanks Steve
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PostPost by: Grizzly » Sun May 28, 2017 4:57 pm

So are you saying it has the stock Throttle linkage but it sticks? from past experience i wouldn't rule out the Carb throttle plates sticking.

I too had a carb rebuilt by a pro and i could only make it idle if i pushed the throttles closed by hand (don't forget due to the type of linkage one carb can be stuck open slightly even when the other is fully closed, that why i had lots of head scratching at first), i checked it by removing the internal return spring and then it was quite obvious the throttles were tight (the Butterfly's weren't fully closing so the idle would stick at 1100 and i also had the throttle stick when i was driving at about 3700). Now it's all fixed my stock throttle works fine.
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PostPost by: Concrete-crusher » Sun May 28, 2017 5:36 pm

Thanks Chris , that's certainly a possibility looking at my bag of bits it does not look like the return springs were changed.

I'm looking at the Haynes manual for webers and it shows a spring behind the plate but I can't see any detail , did you just swap this spring ? Or is there more to it .

Could that also cause the poping

Sorry 2 questions

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PostPost by: Grizzly » Sun May 28, 2017 6:59 pm

I didn't experience any popping with mine....

The return spring lives under the plate i've circled
dcoeinside.jpg
dcoeinside.jpg (64.76 KiB) Viewed 1121 times


It could be replaced in situ with some long nose pliers and a torch but i'd want to check the throttle shaft / Plates move smoothly fully open to fully closed without sticking while the spring was out..
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PostPost by: EPA » Sun May 28, 2017 7:27 pm

Are you sure that it isn't the cable holding the throttle slightly open?
Is the cable still under tension when the engine is at idle?
When my car (plus 2) did this ,it was a problem with the shaft having moved in the pedal box preventing it from turning freely which stopped the throttle returning completely to the idle position . The cable itself could also stick
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PostPost by: vstibbard » Sun May 28, 2017 9:54 pm

check the springs al already suggested, if persists, then check that throttle plate alignment, ideally these are fitted on shafts with screws to secure just off tight, close throttle to allow the plates to align themselves with the carburettor barrels then tighten carefully

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PostPost by: Bill » Sun May 28, 2017 11:00 pm

I had the same problem this spring on my 1600 (26/0538). It was fitted from new with a scissor type of return spring that attached is captive to the throttle cable's conduit attachment point at the throttle operating arm of the webers.

it is a large strong V shaped spring that maintains a positive closing to the idle stop setting.

Mine broke and the internal carb springs are not strong enough to return the cble operating system to idle effectively I found. I would also advise getting a spare 'cause they do break - hell - after 53 years something has to!!

Ken Grey at Dave Dean's knows of it.

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PostPost by: Grizzly » Mon May 29, 2017 2:07 pm

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PostPost by: Concrete-crusher » Mon May 29, 2017 5:11 pm

Having played with the engine today it's certainly more constant without the throttle cable attached.

I had added a second spring and it seems to cause some creep when things warm up.

There seem to be 2 kits available sytec or ttr , I can see the bonnet clearance is tight about 20mm at the front end and around 60mm at the back. Can anyone confirm either of these fit without fouling the bonnet.

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PostPost by: Peter Richen » Mon May 29, 2017 5:45 pm

I have a 65 S2 with Weber Carbs, and also had the sticky throttle problem that you are dealing with.
I added a bracket with a spring (from a local hardware store) to supplement the v shaped stock return spring, but what I think helped the most was taking the throttle cable out and lubricating it by slowly dripping motor oil between the cable and it's sheath.

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PostPost by: Bill » Mon May 29, 2017 7:20 pm

Chris

Yes that is the one - I have had 2 break (in 53 years) I know keep a spare with me.

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PostPost by: cudabenefast » Tue May 30, 2017 11:33 pm

I am in the process of fitting a Mangoletsi cable kit which is just 10mm higher than the weber top and allows infinite (well almost) adjustment of the actuation.

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PostPost by: Concrete-crusher » Wed May 31, 2017 6:34 am

Thanks I checked my clearance by putting a 45mm card on the first carb and a 65mm card on the second carb , balanced a torch and my iPhone under the bonnet and took a video of the bonnet closing.

I'm surprised how much room there is probably about 70mm

So a sytec kit is on its way. Ready for some more weekend tweeking

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PostPost by: nmauduit » Wed May 31, 2017 1:06 pm

cudabenefast wrote:I am in the process of fitting a Mangoletsi cable kit which is just 10mm higher than the weber top and allows infinite (well almost) adjustment of the actuation.

Peter


I got that too, was told that it was lower than the Weber equivalent and it did indeed fit well under the bonnet - well made and no complaint so far (I have not yet installed the dual cable control, just used the stock cable instead).

I recall I did have to file very slightly the manifold web (sand cast ridge) to that there would be a tad larger clearance for the carbs actuating lever.
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PostPost by: cabc26b » Fri Jun 02, 2017 8:30 pm

I have been using this low profile unit from RD for more than a decade - no issues with bonnet clearance and very stout spring to ensure return -
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