Hi all,
first post here, likely not the last.
Recently taken possession of 69 bug, with a 1300 (not original engine, I might add) and a 30-pict-1 carbie. Or maybe a -2. Can't remember now (car not here to have a peek at).
I got the engine turned over, and it idled OK after warming up. It hadn't been started in probably 18 months. Anyway, i tried opening the throttle but it would quickly lose power and begin to sputter out. If I backed off on the throttle, it would recover and idle. It revs only up to a point.
The choke butterfly was fully open and the air filter was off. I thought perhaps a blocked jet?
So I tried revving the engine and choking the carbie with a rag to suck out any blockage. Didn't work.
Any ideas?

Maybe the advance on the dizzy not working

TBH if it's been sitting for 18 months then the petrol will be knackered and can cause it's own issues but it is likely that the petrol has sludged and tarnished the inside of the carb. I'd recommend a can of carb cleaner and a full strip down.

To check if the vac dizzy is working then take the cap off and suck on the vac pipe. You should see the advance plate move. If it don't then try to manually turn the plate. If it turns then likely the vac can diaphragm is perforated. Remove it from the dizzy and suck on it. the arm should move easily and return when you stop sucking. If the advance plate didn't move then it could have got stuck to the dizzy shaft. Soak in Plusgas or similar rust penetrating fluid. WD40 can work but it's a water dispersant and not a rust penetrator.

Another thing is fuel delivery. The pump may be able to supply enough fuel for idle but nothing more than this. Smell if the oil has a petrol odour.

Don't try and cut corners with the carb. YOu want a solid baseline to work from and if you don't give it a proper clean you can be chasing your tail for a very long time

thanks for the replies!

I had forgotten the diaphragm on the dizzy. I'll certainly try the vac pipe. The advance plate did move by pressing it down, but that doesn't test the diaphragm.

regardless, as psimitar mentioned, carbie probably won't be very clean anyway. I've done some reading up on carbie strip-down.

I had thought of the fuel pump being not up to the task, but didn't know how to test it. petrol-flavoured oil, you say? another noob qn- why would this be the case?

its all learning, right?

a pin hole in the fuel pump diaphragm can cause lack of fuel delivery and "petrol flavoured oil" as you put it because the fuel leaks through the pin hole and runs down inside the case into the oil.

Yup, what PV370 said. The only other way to test a fuel pump is with a pressure gauge and then you'll need a t-piece and extra piping. Not something the home mechanic keeps in his toolbox.

Also check if the fuel filter (if fitted) is clean/clear and not gummed up (hard to see). And that the fuel line allows clean petrol to flow out freely (and not water, dirt etc., which can collect at low points).

Drain the tank and put in new petrol

Also as above check the dissy vaccum to see if its working

hey guys,
thanks for the advice,
an update on it: yep, checked filter and replaced (was pretty dirty). Ended up replacing the vacuum line on the dizzy as the rubber had pretty much fallen away. I'm guessing it wasn't making much of a vacuum...
However, was still having the same issue
So, going back to the carbie. Got a rebuild kit. Now just need to take a deep breath and try that.