Carbs from hell

[Johndecarlo]

Been having tuning issues with my motor, relatively certain carbs are to blame, but alas here i am in need of some help figuring this one out.

Dual drla 40s

#3 e tube, 180 air, 135 main, 60 idles, 30 pump jet- thingy-

2110 (40x35 heads)
Cb crank trigger, 15 deg @idle, 32 all in @3k (pretty much stuck with preset dual carb spark map)

And here is whats going on: carb runs a little rich at idle, not terrible tho, however cant get engine to run without exposing the bottom progression hole slightly, in other words cant get it to idle with butterflies fully closed, i would say bigger idles, but im already at 60s and idle is already rich at 2.5 turns out. Anyways, with the car idling@ around 900rpm and carbs in sync, car runs "okay" even "good" at times, but as soon as i get the throttle past about half way between closed and wot, iy leans out, not the accelerator pump, only happens in gear, for example getting onto the hwy, everything is good, go into 4th and start mashing on the pedal, but once i get halfway or above 2500rpm, it jumps from .90 lambda to 1.22+. Done all the obvious lile cleaning carbs and jets, checking for vac leaks, etc... Any ideas welcomed

[67 Sunroof]

Is this a motor you just built? When did it start happening?
Are they the same carbs you had on it before or have you recently changed anything?
The more info (no matter how silly it seems) the better for people to diagnose your issues.
There’s some fart smellers......I mean.....smart fellers here......to help you out.

[QRP]

I'm not much of an expert when it comes to Delortos, more a weber guy.
Acording to my chart you're pretty close to factory jetting.
Have you tried opening the air bypass screws?

[nextgen]

John, when were the carbs last rebuilt. I had a back fire that I tried everyting to get rid of, nothing worked, had the carbs rebuilt and my bug runs great.

I rebuilt carbs but after seeing photos of all the parts and it done by a pro. I knew I as not even close.

Ok also could be fuel pressure, Timing but at $120 per carb, there is a world of a difference. Try the other things first.

Flames were coming out from back fires. Now nothing . Photobucket shut me down, because I will not pay for my free photos they gave me an and now want money to use.

IF you want some photos PM me and I will send them to you. Never though a rebuild would get rid of the back fire 90% of the guys said exhaust leak.
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[67rustavenger]

Do you have a set of .2 emulsion tubes?
The .3's are a compromise between .1 and .2.
What's likely happening is that at medium engine speeds. The carbs are running rich once you have opened the throttle half way.

I run a 2180 with Dellorto 45's. My idle jets are .50 (just verified last night) and run a little rich. .60's on a 2110 are likely very rich.

Good Luck.
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[j-dub]

Exposing the bottom progression hole just slightly is normal for DRLAs.

Leaning out at half throttle sounds like it is not getting on to the main circuit soon enough. What size vents are you running? Are you running the "update" kits by chance? I would also check your float height, if they are too low that will delay the mains.

What happens at wide open throttle? Do the mains work properly then? 0.8-0.9 lambda?

It might also help to mention if this used to run great then there was a sudden change, a change over time or it always had this problem.
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[HBRag]

Lean transition is highly affected by float level. Make sure pressure is 3 PSI +\- .25 and set for 5mm close. I ended up with .3 emulsion for 45s on a 2276, which helped the transition. I still increased the air correction to 200, and tuned for lean cruise (MagnaSpark Digital). With that my transition still climbs from 16.0:1 to the 17.5:1 range, but the car runs fine. Without the floats at 5 mm, the lean hole rises to 20:1 and results in a misfire about 3800.

If you measure down the main jet hole for fuel level, and index the depth on the stack, the fuel level should be just below the first row for four large holes, and above the step.

Short if messing with the progression holes, I think this is the nature of the beast. I didn’t go there because with a lean progression tune, I’m is the safe zone for EGT/Head Temp. With a rich progression tune, the leaning might but you right in the danger zone at cruise.

[modok]

Two key bits of information missing
the venturi size
transfer port sizes, are the top holes 1.4 or 1.8mm?

The first transfer port is only covered when the throttle is 100% closed, so, if you want to idle with the throttles closed you will probably have to drill out the idle mix seat for more fuel and adjust the idle speed with the bypass valves. Or, not, because, WTF

also WHY are you running #3 tubes? is that what came with them or a deliberate choice.

[Johndecarlo]

Thanks for all the input guys, fuel psi is 3 on the dot, even shelled out the big bucks a while back on a precision analog gauge that only reads from 0-5psi, so confident on that, havnt checked float since i first got the carbs a few months ago, but they were fine last i checked, carbs came to me very clean from some ebay guy, alfasomethingorother, good reviews and talked to him a bunch, seemed to know his stuff and honest guy, cleaned them when forst got em and a few times since, including a few days ago trying to solve this. Car drives alright, tbh would only really be able to tell its running lean from the afr gauge, no spitting or anything. But its been like that since i got thr carbs, only now looking into it since i installed a crank trigger with magnaspark and so running more advance and worried about detonation. Built the motor about a year ago, lean condition came with the carbs for sure. Not sure how slightly i can expose the bottom prog hole, any pics would be awesome

[modok]

alfa1750, he knows carbs, does not know VW's tho

This guy was funny, https://www.thesamba.com/vw/forum/viewtopic.php?t=717707&highlight=transfer+port+size
He tried everything else except what I recommended.
lead a horse to water?..... or, more like dragging a mule backward by the tail....politely?

But he sure tried every other idea and found what didn't worked, and kinda worked, so I guess it's worth it.

[Johndecarlo]

Okay so drove it tonight and paid close attention to a few things, leans out based on throttle position, not rpm, in other words i can engine break, without it leaning out, and once im driving, i can get it upto say 80mph in 4th, and let off the pedal a bit but keep the rpms above 2500 or even 3k and it doesn't lean out, but as soon as i hit the pedal a bit and pass this invisible mystery point, it instantly leans out. Also tells me its def not an accelerator pump issue cuz if im driving with the pedal mashed and its leaning out and then let off the pedal some, mixture richens up/ goes back tj where it should be. Other than that, the lean condition stays through WOT. One last peculiarity, as i was driving and starting to push the engine, at about WOT and holding it there, the engine suddenly made what i can only ralate to a big backfire, but just one, one big loud solid BANG, and my car jerked back and forward some, and then kept on going just fine like nothing happened. This was rhe only backfire or anything of the sort. Not since i first built tje engine has anything even similar happened, it was pretty strange tho, didn't feel like the usual lean backfire, more like pressure had been building up in a tank or something and then snap crackle pop, it went bang. Got pretty nervous for a second something serious happened, but as i said drove on just fine, cyl head temp stayed around 350, oil around 180. Any help here is really appreciated

[Johndecarlo]

[Alstrup]

Idle timing is too high. Reduce to 12.
Reduce Idle jet size to 0,58.
135 mains (?) venturi size?

Dependant on which model Dellorto you have, there are a set of bypass srews beside the mixture screws. They may need to be set into action to close the butterfly enough with that much displacement. BGut do the top 2 things first.

T

[Johndecarlo]

[modok]

[67 Sunroof]

What gauges are you using for your a/f ratio readings?
Just curious...

[[email protected]]

you have way too much timing, at both full advance and at idle. That's not helping. Go back to 28-30 total, 8-10 at idle. Then re-tune the carbs.
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[Johndecarlo]

[[email protected]]

after changing the timing, did you re-tune the idle speed and idle mixture on the carbs? You need to.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[Johndecarlo]