Tried all, persistant 34 pict3 flat spot

[autocrat]

HELP! flat spot, tried everything, 3 mechanics
Read many posts about common 1600 DP, PICT 34-3 carb flat spot.
My 72 Super; newly rebuilt 1600, typical flat spot and poor idle. 
I replaced the 009 with a new SVDA, then a new DVDA.
Replaced the Brosol carb with a rebuilt German Solex. 
This made the car run better, but still had flat spot. Idled well.
Decided on taking to a mechanic.
First ACVW mechanic tweaked the carb, checked timing, valve adjustment, said it was as good as it would get. 
2nd ACVW mechanic ( seasoned vet who said that VW was embarrassed with flat spot issues when the new '71's were introduced) finally gave up after;
Replacing the fuel pump, old one putting out too much pressure and outlet tube was loose
Bypassing the fuel tank and lines with clean fuel from gas can.
Checking and re-rebuilding the Solex.
Putting known good coil, carb and DVDA distrib on car in place of mine.
Check timing, etc., checked for vacuum leaks on intake.
He gave up in exasperation.
The engine fires right up and idles well, runs well once the bog (right off idle) is passed. The flat spot makes the car no fun to drive, to put it mildly. I'm starting to lose patience and interest in the old Super Beetle.
Bogs after every shift, naturally most noticeable off the line.
What else would cause this?
My next step is to pull and replace intake, mechanic said car ran and idled too good to have significant vacuum leak in intake, and he checked it. He also said that the new DVDA distribs were junk.
Thanks for any help!

[harryset]

You've changed carbs so this is a stretch: Check the hole in the butterfly and make sure it is the right size. Some butterflies have a hole that is too big, insert a pop rivet and flat spot is fixed.

Two mechanics have reset the timing, to what? Timing should have been set at full advance, around 3000 rpm's.
_________________
'72 Standard
Proud owner of a "Hoover Bit"

185 60's up front, Empi disc kit, 2 1/2" drop spindles, 185 65's in back, stock drums.

Sound Deadening by Secondskin

[TrikeKid]

Got carb pre-heat? If the intake is iced up the car isn't going to care what else you changed.
_________________
'74 Baja - The Snowagen
'88 Suzuki Samurai - The endless project

That'll buff out... with a sawzall.

[airgrabber]

Dont know if this will help but here is a sight I found...

http://www.aircooledtech.com/34pict3_modification/

[harryset]

Last place you'd think to look, the faq's

http://www.thesamba.com/vw/forum/viewtopic.php?t=365762&highlight=rivet

You can start by looking down inside your carb to see if you have the big port or the small port.
_________________
'72 Standard
Proud owner of a "Hoover Bit"

185 60's up front, Empi disc kit, 2 1/2" drop spindles, 185 65's in back, stock drums.

Sound Deadening by Secondskin

[autocrat]

The carbs have been ruled out, I've seen the pop rivet fix and have exhausted searching, but I do appreciate the input.
TrikeKid, I think you're onto something with the pre-heat, I'm going to try another manifold, and see if that makes a difference. I'll post the result.

[djkeev]

[candymustang65]

Pre heater again ?
You gotta be kiddin me ?
Season'ed ACVW mech ?
Guess he didnt get my Samba memo on plastic inline fuel filters in the engine compartment .
Im in So Cal and I really am a Seasoned ACVW mechanic and Muscle car Mech and Deisel Mech and ? and ?
But Im thinkin I would be $cratch ahead of the game if I just blam'ed it on the 009 dizzy flat spot .
Good Lord know's Im tir'ed of fixin samba screw up's ?
Rivett's in the throttle plate ?
Are you serious ?
Im in Roy Rogers ville area in So Cal contact me and bring me your carb .
No Charge !
Or just continue to blame the 009 dizzy flat spot like the rest of these knuckle head's ?
Yeeesshh get's any worse in here Im not gonna be able to honestly reccomend the Samba as a place to get good V.W. Information .
" I rebui;lt the carb 5 time's and then bought a new one but it still keep's die-ing out at stop sign's and it hesitate's on take off . "
Typical Samba help in this forum ?
Yes the 009 has an inherent flat spott .
But for the most part it isnt even noticeable and I doubt seriously the hesitation you describe is caused by the 009 .
The 009 flat spot can be tunn'ed out to being barely noticeable if at all .
tweeking can cure it alltogether .
In fact 009 flat spot is the excuse that non knowledgeable mechanic's use to explain to there customer's why they cant fix there car .
Gunk , Gunk , Pop verrrrrraaaaaaghhhhh ? LMAO
Samba need's to start a Girl Scout forum for these clown's ?
Sean

[autocrat]

I spent the afternoon cleaning the preheat tubes on the other manifold, it'll be clean when I do the swap next weekend.

[jbrandt01]

I didn't see anything about the valves being adjusted or checked. While your at it give a good look to the condition of the head, check for cracks and loose studs. Since your down there, check out the condition of your ground strap.
_________________
1972 VW Super Beetle (Turbo + EFI)
2010 VW Jetta TDI

[autocrat]

Thanks for the input. When i find the problem I'll post it as solved. Valves have been checked, head bolts, I'll take a look.
Still haven't changed manifold...life gets on the way.

[flyboat]

Check this out. It may help
http://www.vw-resource.com/34pict3.html
I had a flat spot in my 34 pict and could not get it out. I did not have this info at the time. Here is another post referring to carbs and dist. that may help as well good luck
http://www.thesamba.com/vw/forum/viewtopic.php?p=5017849&highlight=#5017849
_________________
79 super Vert
62 Ragtop Bug
66 tintop Westy
Porsche 914
09 Z06 Vette track car

[danny1940]

I just rebuilt a 1971-1600 to 1641 with new carb and flat spot. I simply eliminated the problem by adjusting the accelerator pump arm to push more fuel. Everything else was in spec before I did this and my flat spot is history. Good luck, Dan

[autocrat]

Just changed the manifold, this one's carb heat tubes are open. Found a tear in one of the silicon boots. Thought this would be the answer. Changed the manifold gaskets also.
Flat spot still there.

[HRVW]

Danny above hit the answer right on the nose. The adjustment of the pump rod stroke is what I did for many yrs. The small nut has to be loosened and the adjustment moved one notch towards yourself if my memory serves me right. Gives a longer stroke/pump action.

Did the same with my Weber DCOE sidedraft Turbo setup. Longer stroke was needed....more fuel on exceleration with the throttle open.

Strange how so many are making the 009 a scapegoat when the 34-3 Carb was the problem... (sometimes).

[GTMike]

Ok, lets take it back to the beginning. First who rebuilt the engine? Was it professionally rebuilt? did you rebuild it? or did you purchase a long block and assemble the rest yourself?

-MT

*edit*
Ok, the above post was made just before mine. I do to also agree that adjusting the accelerator pump may be your issue, but I guess what I'm getting at is making sure whoever built the engine didn't miss anything and there are no vacuum leaks around the heads or cylinders. But now that I think of it, it would run like crap all the time if that were the case.. (just talking out loud)

Try the pump on the carb first, see if that does it. Turn the plastic nut a couple turns and see where you end up.

[donbarnes]

I was having the same bad flat spot with a 1600dp and also no top end and running lean, kept looking at all the old posts on here, had a brand new Bosch SVDA, kept trying to tune, cleaned out my heat risers, etc...
Finally got mad and tore all three of my 34-3's apart at once looking for differences. I put one carb back together with a 150 main jet and larger air correction jet that I found in one of them, then I soldered the bottom plate closed (couldn't figure out how to get it back in with a rivet in it) and redrilled it to 2mm.
When I put that carb back in it was like a different engine, runs/tunes/idles perfectly now
_________________
Hater of cheap parts and poor workmanship..

[donbarnes]

I had also tried changing the accel pump settings multiple times, and it would seem to help slightly sometimes, but not consistent...Also, of the 3 carbs I have (2 Solex and 1 new Chinese) the smallest bottom plate hole I had was 3mm, so I sized it down to 2mm like the posts on here say. I also suspect I could get by with a 132 main jet as mentioned on here, but only had a 150.
But with those 3 changes- main jet, air correction jet, bottom plate- it will now idle all day then instant acceleration when throttle opened, and it cured the icing/sweating issues the carb was doing also. Before that I was at the point of pushing it onto the vacant lot next to me and throwing a match in it
_________________
Hater of cheap parts and poor workmanship..

[DrDarby]

I usually up the 127.5 main jet to a 130 or 135 and that normally does the trick BUT the ultimate old school trick that I promise will fix it is to pull the accelerator discharge tube off the carb and using a small jet drill, drill the discharge end of it open the next size bigger than it is now.
_________________
Midwest Autosavers, Inc. Crystal Lake, IL

[autocrat]

As you can see from the original post date, it's taken me awhile to get the time to work on the flat spot. I had a bum starter to deal with, and I've been working on the interior. The engine long block was rebuilt by a shop in LA., but the warranty time has run out. I will eventually solve this and post when I do. Tweaking the accel. pump will be next, but I still think there's an elusive vacuum leak somewhere!
Thanks for all the feedback.