Ideas on my dead spot as I accelerate?

[SteelersBus]

2000cc engine
Solid Lifters
Dual 40mm IDF Carbs
SVDA Vacuum Dizzy w/ electronic ignition
Bosch Coil
Bosch Plugs
Bosch Wires

Background...After 8 yrs and about 30,000 miles, I wanted to rebuild my carbs. They had some "gum" buildup on the outside and seemed to need synched often. So, rebuilt the carbs.


Symptom that arose after the rebuild...

Bus will start with no issues. Sit and idle perfectly.

I start to accelerate and have dead spot. If I slowly accelerate, it is very evident and bogs out before accelerating.
If I give a heavy "gas" and allow the RPMs to raise before letting out the clutch completely, it seems to "get passed it". Like a heavy foot acceleration makes it less noticeable. But a slight or slow acceleration makes it happen.

Also, before, when in fourth gear, I could (on a flat road) allow my RPMs to drop low and almost enough to shift to third. But a nice easy acceleration would bring it up to acceptable RPMs to stay in fourth. But now, when I try to do that, it will do that flat spot or dead spot as I try to stay in fourth rather than downshift to third.

The only change was the rebuilt carbs. I then checked and adjusted valves. Also, tried to tune the issue out of the carb. No luck.

Hope that makes sense. Any ideas?
_________________
Volkswagen Locksmith
25 yrs experience
Keys by Code, Locks & Keys Supplied,
Key all your Locks to one Key.
[email protected]

Granny Grose's Buses 19
May 30 - June 2, 2024
Millmont, PA
https://www.facebook.com/groups/333391253346965/

70 Campmobile, 70 Sedan, 71 SO-69 Westy, & 74 Westy

[BUSBOSS]

Wrong jets?
_________________
All the redemption I can offer, girl, is beneath this dirty hood
1976 Westfalia
1970 Karmann Ghia Convertible (sold - but not forgotten)

[SteelersBus]

[SGKent]

First check the timing to be sure it is advancing. If it is leave it alone for now.

Likely something is either wrong with the sync or you did not get the accelerator circuits correct - missing check ball, wrong diaphragm in the kit, wrong linkage hole etc. The mixture is going way lean when you step on the gas. You can also check the pump nozzles to be sure that they spray a good flow when you open the throttle with the engine off. Alternatively if it isn't there then your high speed mixture is off, which would be unusual if you didn't change jet sizes or emulsion tubes etc.. Did you get the float level set? Does the fuel pump have good pressure?
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[orwell84]

It could be a lot of things, which can happen when a lot of stuff gets pulled apart. Go through the basics, including fuel pump output as well as regular tune up stuff. Knowing what it’s not is almost as good as knowing what it actually is. Sometimes when rebuilding carbs, crud gets dislodged and blocks something. Linkages wear, get sloppy and don’t stay where you put them. You get the idea.

[timvw7476]

Check the manifold gaskets at the head to man. junction. Those things love to loosen over time & leave a tiny leak leading to subtle vacuum issues.
Also everything connected to the power brake servo/collector.

[germansupplyscott]

Float level?

Your note above refers to float assembly. Maybe the wrong height adjustment so the bowl is not as full as it should be, or too full.

Do you have any way to measure A/F ratio while driving?
_________________
SL

[aeromech]

A lot of dune buggies use these carbs. They have air jets that get dirt in them. Small dirt plugs these jets and then you get the stumble you’re having. The fix? Unscrew the jets and blow out the crap. If you know this fix then you can continue your day and have fun.


Link

_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound