Lotus Elan

Engine Idle Speed Again

PostPost by: Concrete-crusher » Thu Jul 11, 2019 10:24 am

I have checked the vacuum hoses , no leaks as far as I can tell , the lights stay up for ages when you switch off the engine so a good sign.

I have run oil around the inlet o rings , no signs of smoke or engine speed change when I tried it with carb cleaner.

The jets are new , and driving / acceleration is really good.

The balance from rear to front at 950 rpm idle using a synchrometer is 5 , 4 , 4 , 4

I don't think there is much I can do to improve the rear carb.

below is a picture of the idle screw. Probably a daft question but is there any benefit in fitting a second idle screw on the from carb ?

img_1123.jpg and


thanks Steve
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PostPost by: rgh0 » Thu Jul 11, 2019 10:56 am

I would also check the throttle butterfly versus the progression holes at idle as a partially exposed progression hole can result in higher idle

cheers
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PostPost by: Mick6186 » Thu Jul 11, 2019 2:30 pm

On my dellortos the screw you show in the picture is the balance screw not the idle adjust.
If weber are the same twiddling the pictured screw will adjust the idle, but also ruin the balance,
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PostPost by: Sploder90 » Thu Jul 11, 2019 2:36 pm

Could it possibly be leaking air at the butterfly spindles and leaning off the mixture?
As I understand it there is an upgraded bearing with a better sealing arrangement. Have seen them on the -bay but have no experience of them.. I've got a bit more work to do before I get to the Weber fiddling point
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PostPost by: joe7 » Thu Jul 11, 2019 3:04 pm

I think your thackery washers look a bit too tight.
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PostPost by: Donels » Thu Jul 11, 2019 4:19 pm

Check that there is a little play in the throttle cable. If it is too tight the outer sheath can expand more than the cable and open the throttle slightly increasing the idle speed.
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PostPost by: pharriso » Thu Jul 11, 2019 5:56 pm

Next time it idles too fast, hook your foot under the throttle/gas pedal & pull it fully up. If the idle speed goes back down something in the throttle mechanism is sticking.
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PostPost by: billwill » Thu Jul 11, 2019 8:03 pm

Mick6186 wrote:On my dellortos the screw you show in the picture is the balance screw not the idle adjust.
If weber are the same twiddling the pictured screw will adjust the idle, but also ruin the balance,
Mick



The actual IDLE SPEED setting screw is a vertical screw on the right hand side of the rear carb. It presses on an extension piece of the throttle mechanism and merely acts as if your foot is pressing the throttle pedal slightly. Your photo shows a non-standard version of the IDLE SPEED setting screw at the bottom edge of your photo.

As Mick say the main one you show towards the top of your photo, is the balance screw which you use to get the two front pistons working the same as the two rear pistons.

To answer your original question, there is no point in having TWO THROTTLE IDLE SPEED Set screws.

~~~
You don't seem to have a throttle return spring to close the throttle when you lift your right foot.
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PostPost by: billwill » Thu Jul 11, 2019 8:14 pm

This picture from the gallery shows the standard Dellorto setup, but the Weber setup is very similar.
Image
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