Dellorto Help Required

[Spydaman]

I've got a mild 1776 Beetle engine with 40 DRLA's in the Bonito and am struggling to get rid of a lean area at the transition from the idle to main circuit. I've got an AFR meter so can see exactly what's going on but can't seem to fix it. Idle is 13.5 -14.0, Cruise is 16.0 - 17.0 and WOT 12.7 - 13.5. The problem is it that leans off to 19.0 at the transition when the throttle is eased open. I reckon the main circuit isn't coming in early enough which should be cured with smaller air correctors but this doesn't work. Current set-up is as follows:
Venturi 30
Idle 52
Main 122
Air corrector 160
Accelerator pump 45
Emulsion tubes 9165.2
Ignition 32BTDC all in by 3000rpm plus 10 degrees at cruise.

Any Dellorto experts out there offer suggestions?

[Spydaman]

Thanks for the reply.
My understanding was that smaller air's create more suck on the main circuit bring it in earlier. I agree they also limit the air at WOT and need the adjust the main jet accordingly.
Yes I meant 9164.2 General consensus is that they work best for Beetle engines. I've tried 9164.1 .2 and .3 but none get rid of the lean area. I've also gone up to 60 idles which just make the idle circuit very rich.

I'll give it another go with the 9164.1 airs and bigger idle jets.

[Spydaman]

The carbs came with 35 pump jets and again the consensus is 45's work better. I've tried the 45's with the volume set I think to 2cc/10 squirts.
The float level was a mile out but is now set to 5-6mm between float and cover.
I'm beginning to suspect low fuel pressure not keeping the float chamber full but it seems ok at WOT so maybe not.

[spydaman]

I've got some 28mm chokes which I also tried. Maybe its time to start again from first principles.
Venturi 28mm
Main 112-118
Idle 50-55
Air 160-170
Emulsions 9164.1-2

100bhp at 5000rpm would be nice and probably achievable. Carbs clean and unworn so suspect jetting rather than blockages/leaks.

[Spydaman]

Definitely steady state. I can hold it at 15-16 cruise then ease the throttle open and it goes weak at 19 until the mains come in at 12.7-13.5 If I boot it it'll accelerate through without hesitation.

[Spydaman]

Based on your recommendations I've gone for:
Chokes 30mm
Mains 130
Idles 55
Air Correctors 180
Emulsion Tubes 9164.1

If that doesn't work I'll try 28mm Chokes

[Spydaman]

Better but a bit rich everywhere and it's still flat at the transition from idle to main circuit.
Idle mixture 12.5
Cruise 12.5 @ 3k rpm, 19 @ 4k rpm
WOT 11
It doesn't seem to respond as it should which makes me suspect it's something else. There's O ring seal on the auxiliary venture. It looks ok but if it doesn't seal 100% it will reduce the vacuum signal the main circuit?

[Spydaman]

Thanks for that. I had a read through it and believe it refers to the progression from idle mixture to the progression drillings/idle jet whereas my problem is the progression drillings/idle jet to main jet circuit.
I found this http://www.datsun2000.com/tech/weber_tuning_method... which suggests that changing the air corrector adjusts the point at which the main circuit comes in. The consensus is that 180 AC work best with Beetle engines but I've also read that the AC should be the main jet plus 50. I'm now using 130 mains and 180 AC. I've tried 175, 160 and 200 but none have the desired effect which makes me think it's something else.
Until I fitted the AFR gauge I never new I had a problem but now I have I can see and feel it goes flat at that point.

[Spydaman]

Yes, I know I can set the idle mixture to whatever I want. I wasn't saying it was fixed at that just that 12.5 and maybe a bit weaker gives the most stable idle.

I think 7850 is for a DHLA. I've got DRLA's and there is only one size idle jet holder.

Edited by Spydaman on Thursday 25th June 14:23

[Spydaman]

I've got a pair of 36 DRLA's but only have 30mm chokes for them. I've also got single 40 DRLA on a manifold but they're not supposed to be very good due to the length of the inlet tract. I guess the next step will be 28mm chokes in the 40 DRLA's with jetting to suit. If that doesn't work try the 36's. If they don't work I'll have to live with it. I won't be able to try anything for a couple of weeks as I'm holiday at the weekend. Thanks for all the advise and education.

[Spydaman]

I believe my problem is the transion from the idle circuit to main rather than idle mixture to idle cicuit. Looking at the progression holes it looks like it has the full compliment already and as you say it's a bit difficult to make holes samller if it doesn't work. I think in the first instance I need to get a bit more suck on main circuit a mid throttle to get it to come in earlier. Or extend the range of the idle circuit so it overlaps the main circuit. As Pumaracing says by reducing the choke size.