Octane?

Plugged idle jet. 95% sure.

I second the idle jet being plugged , If I recall correctly, you run to about 1300rpm before you transition to the main jet.

1,300 rpm to transition over to the mains sounds really low.  That would be just coming off idle for most of us, right?  More like the transition starts around 2,800 and is on the mains by 3,200 rpm.

But that's not the problem......the problem is a clogged idle jet, and like Stan - 95% sure.

Ditto.  Plugged idle jet(s).  Welcome to the Wonderful World of Webers.

Google "Jet Doctors". They could be the answer to clogged idle jets. I had them installed on my 44  Webers and no trouble yet.

I agree that you have plugged idle jets.   One of the biggest problems with plugged idle jets is gunk laying on the bottom of the carburetor air cleaner base.   Jet Doctors help but remove the air cleaners and clean the base of any foreign or ""domestic"" matter. 

I've had Jet Doctors from the beginning.  They are great in keeping the shmutz out that Larry talks about, but they don't help with gunk in the fuel, much of which comes from ethanol attacking fuel system components.  That's been most of what I've had to fight.

Ethanol nibbling away at my peace of mind, huh?

Marksbug solution of three transparent fuel filters might be a veeeery good idea!

Maybe four is even a better idea: one exiting the tank, one before the fuel pump, and one each to the carbs. 

Run the fuel out of it. You may have accidentally put 87 octane in it. Also the station that you filled up at may have accidentally put 87 in the 91 tanks. It happened to me before.

I'm sure you already checked this but make sure your intake manifolds are not loose.

Oooo yeah, I forgot about that one.  Really made a difference when I fixed that.

Rusty, I certainly hope that it's just a coincidence that the engine began running crappy after that 92 octane fillup...and that gummed up idle jets are my problem...because I'd hate to have to siphon $30 out of my tank!

The octane selection is via a big prominent push button...There's no way I accidently made a mistake.

The station has inground separate holding tanks for each octane. The manager told me that each delivery has verified paperwork confirming total gallons/octane that prevents mix ups and allows them to check volume of previous fuel sales....but for some reason she can't find the most recent delivery paperwork!

I'm aware of the fact that the delivery tanker seems to not have separate cells for different octanes...and that modern auto engines handle both 87 and 89 octane without a noticable operating difference except for gas mileage.

Could it possibly be that to get them through the day that some 87 was mixed into a low 92 holding tank?...I'll certainly never know, but if clogged idles isn't the problem then I'll start looking for a gas station that doesn't misplace their delivery paperwork!!   

or crap in the fuel. did you realy expect the gastation to say "why yes we sell **** for fuel and have had oh so many complaints" well it is thier responcability to make it right...if it is thier issue, but it's not the octane, probably idle jet or water or something else. you can run some cleaner through it,I like the berrymans fuel injection cleaner, stay away from the luscass crap and no name stuff.chevron techron is also good, but they wont clean out a cloged idle jet. and sometimes if the motor farts,sneezzeess, burps,snaps,backfires just 1 time it can blow a peice of intake gadget out and that will also cause issues. as for the "flatspot" it probably isant the carbs but rather the dist addvance curve.

  the spudering in gears sounds like watter in fuel or sparking bolt dead, or wet dist cap or plug wires.or even a plugwire has fallen off ah duh ting.

  just by chance do you have a fuel filter on it?? a clear one that you can see if there is watter in it?? or pull off the one you have and empty it in a glass jar, empty it from the end that is coming from the front of the car to see whats in side, you may want to just get a new one first&put it on as you remove the old one.I use 3  on my stuff.1 befor the fuel pump at the frame horns and 1 before each crab after the das fuel pumpkinhousen.

Okay.... here it is... one of my embarrassing stories. I bought the Weber carburetor book from CB Performance so I could do my own tuning. I started throwing the carbs out of tune and sync then would real it all back in. I'm sure most of you have all done this.

Well during one of my little learning experiences I filled up with bad gas but I didn't realize it. Now I spent many fricken hours trying to fix this problem. Doing everything by the book but having zero success. I made some shout outs, but not to people that knew me because I was pretty embarrassed that I couldn't fix it myself. So in-the-meantime I drive the car. A week passes and every night after work I'm screwing with the car. "Dinner's ready". "Okay I'll be there in a minute"... You get the picture... "Dinners cold. I'm not going to fix it for you if you're not going to eat it!"... Damnit.  

So... I'm workin' on it and now almost out of gas. I'm quite aways from home over in a business complex after hours. It's getting late. I'm trying to tune this thing away from neighboring ears... it's dark now and the batteries in the flashlight were about dead, my patience and temper are in check. I finally gave it up and decided to head for home. I came around a corner and damn if I didn't run out of gas. I coasted to a stop.

Okay... Exxon station within eyesight. I called them, "Do you have a gas can I can borrow?" In a foreign accent, "No. But we do have one that you can purchase!". Called home but no answer. Okay... Fine. Fine!!! I get out and began pushing... I started thinking about all the milkshakes, the double-double cheeseburgers, and all the other crap food that I have ingested over the years... I stopped, very pissed off now. I resigned, got back in the car. "F-it! I'm not 20 anymore but knew that 30 years ago I could have easily pushed the fricken car up that hill and into the gas station parking lot and not had a massive heart attack doing it.

I called home again. No answer. So now I'm calling AAA, I let them know where I was. Called home again still no answer. Thank goodness because I was really pissed off. Within 30 minutes Dunivan's calls me. "We got a tow truck in route". "Great" I said. "Hey I don't know if you people do this or not but I have a car that uses 91 octane gas. Can you bring a gallon or so of that?". "Yes we can".

Another 45 minutes goes by... people are walking past, several "Nice car" and "Thanks" take place but I don't want to talk about my car and it must have shown through my bad attitude so people just kept going. It's now 10:40PM the tow truck guy arrives and he apologized for taking so long. "I had to stop and get some 91 octane gas. Nice fricken car man!"... "Thanks". He poured 2 gallons in and, after a little cranking it started up. I knew in an instant what was up. I had everything adjusted properly and now the car had the kind of gas that it liked and it ran perfect. PERFECT! SSSSH!T!!! I was glad and pissed off at the same time.

I didn't pull into the Exxon station as I rounded the corner on my way home, rather, I stuck my middle finger up in hopes the attendant was looking.

So there it is. From genuine experience... It may very well be your GAS. 

True story....Bought  a Dealer new '73 Beetle, my buddy and I promptly ran it out of gas on the Interstate, we hiked up the highway a bit to the local Shell gas station, hopped the fence and asked the gas jockey to borrow a can and get a buck's worth of gas ...NOPE I need a $50.00 deposit.... who the hell had a spare $50 back in '73?

So pissed off, we start to high tail it back over the fence when my buddy say's "Hey that's got to be the asshole's ride over there... it's the only car there". I grab an empty quart oil can ( remember those?

) from the gas station trash,  jambed I don't know what it was into the bottom of HIS cars gas tank, got our "to go juice" and were soon on our way....

My dad had a '56 Beetle. No gas gage. When it coughed you just turned a 'reserve tank' lever and continued on your merry way for at least 20 more miles.

So sorry about that "no borrowed cans" policy. I was a pump jockey all through high school and college and that was the rule--I didn't make it up. We needed a ridiculous deposit for our one giant "borrow" can and we sold one-gallon cans for about three times what they'd cost in any store. There wasn't a lot I could do to help an out-of-gas person either, since I had to be at the store by meself. It sucked. Hell, I sucked.

To my knowledge, we never sold any "bad" gas. But there is a gas black market. People do steal wholesale fuel and gas that municipalities and states have in their depots. Usually it sells for about 75 percent off. It was happening with the sole source state vender here in Maryland a few years back. Very shady goings-on, and never really solved cause the driver kept his mouth shut. . . .

Since there is a black market, there could be the occasional adulteration. 

I'm still betting idle jet though.