Strange Sputtering

Let me start by saying I

I think the reason you are getting no response from other readers is that is that there are so many possinbiliities.
This is a matter of starting with the most basic things and working up. As is so often said here, check the stuff that is unlikely to cause intermittants----first valve adjustment, then timiing. If elcectrical and valve adjustment is OK it is a matter of fuel. My own experinece is idle jets, which is really a misnomer cause the main does not really kick in till arouind 3500 RPM. which is why it takes off strong when you get past 4k. Pull the idle jets and blow them out really well. Disconnect the fuel lines and blow them back into the tank. Invest in a new fuel filter for a couple of bucks. YOu did not say if the gas was fresh. If it was 6 months old then that could be the problem. It will smelll like varnish instead of that nice gas smell we all came to love when pumping our own.
Another thought is that a 120 main seems a little small even for a 1641 IMHO. WHat is the size of the idle jet. It should be a a 50, again IMHO.
THE GOOD NEWS. This is the kind of simple problem taht any mechanic worth half his salt can track down in less than an hoiur,. TO fix may take longer but at least you know where you are at.
Welcome to old school technology!

Shoot! Re-read your post and I see you did most of what I suggested, except the old gas. Sorry. YOu have done everything I woudl have tried. I will say I am suspicious of such a large air corrector on such a small carba and engine but I am reaching here.
WHat I used to do in situations like this is take it to a place with an engine analyzer and with someone who knows how to use it. Had a 5.L Ford that had the same symptoms many years ago. Replaced everything---carb, fuel pump, plugs, filter, wires etc. It was the distributor --specifically the shaft bushing was worn out. $12 for a new dist---don't laugh, it was 35 yrs ago---and that Falcon Sprint really pulled with all those new parts. IT sure hurt to have spent the equivalent of $300 for a new carb when the old one was just fine. There comes a point where one has to say uncle and go to the guy who has the $50,000 engine analyzer.

Go to your local auto parts store and get a fuel pressure gauge and check your fuel pressure. It should be at least 3.5psi. I'd start there.
Ron

An update.

Over the weekend I did get a fuel pressure gauge and it's testing out to about 4.25 psi.

The gas is fresh.

I also checked the float level... both dead on at 6.5 mm.

I got a tip from someone to try spraying carb cleaner in the carb when it starts to sputter, if it smooths out then it is running lean.

I gave it a try and sure enough if I spray carb cleaner in either carb when it sputters, it smooths out.

I guess it's on to new jets.

I did some poking around and found that CBPerformance recommends:

1.35 mm main jet
1.60 mm air corrector
F78 emulsion tube
.60 mm idle jet
.50 mm pump jet

Seems like a good place to start, what do you think?

I'm also open to suggestions on good VW tuners in my area. I live in WV very close to Cumberland, MD.

Thanks for your help,

Paul

Funny you mentioned it, but Jets are exactly what I suspected when I first read your post. I used the jets out of the box with the ICTs (130s), installed the ICTs, sync'd the linkage, adjusted the carbs, and it ran out of the box on a 1776. If you still have the 130s you might want to try them.

I purchased the car used and the jets that are in it are all I have.

Got the new Jets and rebuild kits on Saturday, and rebuilt the carbs.

Not very difficult and what an improvement.

I still need to do some fine tuning, but the sputtering is gone!!! :D

Thanks to all for the help.

Paul