Lotus Elan

Dellorto DHLA Pump Jets

PostPost by: alaric » Sun Sep 25, 2022 7:01 pm

Hi Roland. Ok, I'll check too then. We'll get there :).

All the best.

Sean.
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PostPost by: andyelan » Sun Sep 25, 2022 7:13 pm

Hi Guys

It says at the beginning of the video that its an 1300cc Alfa engine they're working on.

Andy
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PostPost by: alaric » Mon Sep 26, 2022 12:19 am

Hi again. The fumes must have affected my ability to sleep....

Anyway, searching on this forum I've found the following in a thread from 2012:

"The generic set-up for a new-in-the-box DHLA is 8cc in 20 strokes, but settings for specific engines may vary from that value as required. Lotus' spec for the standard Elan, for instance, is 7.5 cc."

The thread is "Adjusting the "squirt" on dellortos", and the post was by Esprit2 » Thu Sep 13, 2012 10:23 pm.

So, my understanding of that is that the pump delivers 8ml, or cc if you prefer, of fuel in 20 pumps. So, that's 20ml of fuel in 50 pumps. I've adjusted my carbs to 19ml of fuel in 50 pumps. In the video link the adjustment gave 15ml in 40 pumps, which is slightly lower than in the post from 2012.

As advised in the 2012 post I'm going to see if the engine falters at just over 3k rpm. If it does, then I know why and will whip the carbs off and increase the volume slightly.

Regards.

Sean.
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PostPost by: alaric » Tue Sep 27, 2022 6:26 pm

Hi again. So I fitted the carbs, connected the fuel line, turned on the ignition, and watched fuel come out of the back of one of the carbs. Bother. I checked and found the offending carb had lots of fuel in the float chamber. So the new valve appears not to be working too well. Hopefully an easy fix - put the old valve back in haha.

I haven't checked yet, but is it possible fuel can come out of the choke circuit before the float chamber is full - I can't remember where the feed to that circuit comes from - I think there's a jet for it so that shouldn't be the problem. It's the one that I didn't take apart, so I'm wondering if there's a problem in there now - I may have squirted some dirt into the valve...

Sean.
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PostPost by: Roland » Wed Sep 28, 2022 3:06 pm

Sean,

I have now fitted new pump jet NRV's (inc. o rings) and new ball bearings below the pump jet weights. This has improved matters a little and I have an 8mm stroke length at the lever on both carbs.

Rob at Eurocarb advised that I should not worry if the stroke length was longer than 5mm as long as the pumped volume for the jets was correct and consistent. He confirmed the pump volume per jet is 8cc over 20 strokes for my Sprint Engine.

So I think I shall call this one closed.

Roland
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PostPost by: alaric » Thu Sep 29, 2022 5:40 am

Hi.

Rob is very helpful and certainly knows his onions. I swapped the float valve back to the original last night and now all is fine. The engine started first turn. So I'll set the carbs up and go for a spin this weekend. Fingers crossed haha. I won't be surprised if I'm taking the carbs off again...

All the best.

Sean.
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PostPost by: billwill » Thu Sep 29, 2022 11:13 am

Roland wrote:Sean,

I have now fitted new pump jet NRV's (inc. o rings) and new ball bearings below the pump jet weights. This has improved matters a little and I have an 8mm stroke length at the lever on both carbs.

Rob at Eurocarb advised that I should not worry if the stroke length was longer than 5mm as long as the pumped volume for the jets was correct and consistent. He confirmed the pump volume per jet is 8cc over 20 strokes for my Sprint Engine.

So I think I shall call this one closed.

Roland



8cc is enormous for such a purpose, did you mean 0.8 cc ?

Oh.. 20 strokes, so 8/20 i.e 0.4 cc per stroke.
Bill Williams

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