Wobbling engine

So yesterday i set the carbs cold for fast idle, which is fine, balanced them with the synchrometer. I let it warm up and adjusted the idle adjusting screw, one side was nice and responsive, the other one was not, and it was hit and miss turning in either direction. So i managed to get it somewhere suitable, and now the engine is wobbling. Before it didnt wobble.

What could be the cause? I wish i had left it alone now.

 

I suspect one side of your engine is trying to run faster than the other.

 

i reckon i might just get some webers. i am fed up with trying to make old stuff work and finding bits broken all the time. lol.

 

and i have read this - http://www.vw-resource.com/engine_wobble.html

its not leads, and not leaks, and sure its not compression, although will check again. the side with the dodgy carb had sooty spark plugs.

 

You might have a fuel dribble on the sooty side so the mixture screw is not adjusting much.

 

what does that mean?

 

The needle valve in the sooty carb may be leaking or the float is sunk or the fuel pressure is a bit high.
So one carb has fuel coming out unmetered into the venturi as it overflows from the float chamber.

 

clean the plugs and swap them over
restart the engine and let it warm up for a good ten minutes or so
take the plugs out and clean them again
disconnect the linkage on one carb
restart
set the idle speed to about 1000 rpm on one side via the throttle stop...read the sync
set the other to match
rev it a few times then re check the sync on each side

now you can tweak the idle mixture screw (s) for the highest vacuum reading on the sync
repeat for the other carb

lower the idle speed via the throttle stops slowly, until the engine smoothes out
reconnect the linkage and recheck for sync


if it still refuses to play ball, and you're 100% sure all spark plugs are good, suspect a blocked idle jet, worn mixture screw or an air leak

setting the linkage is as critical as the idle mixture

 

You can't balance it on choke. Warm it up until the chokes are completely off, then balance, then set mixtures, then check balance again.

 

Can't get it to balance. Rhs has higher vacuum but it's not wobbling now. Just in different MOT station now and he's passed it.

 

Are you sure it's running on 4? Try disconnecting HT leads one at a time and see if any of them has no effect. You might be supprised at how well they can run on 3.

 

Very true, I had the same issue, was only running on three but sounded like 4

 

And what was the culprit?

 

Did you know your idle stuff is a two part job?
You have an idle circuit - that's the pipes joining the manifolds across the engine under the filter. It's fed and controlled by the big screws on top of the left carb. Speed and mixture. This lot accounts for approx half the idle revs. It has it's own cut-off valve which is the one furthest away as you look in the hatch. If you disconnect the wire, the revs should drop to about 450rpm (slow!). You can then adjust the mixture screws you'll find on the outside of the carbs at the bottom of the carbs facing 45 degs towards the front of the van. Also you may have to over-set the throttle stops to keep it running while you do this, but when it's correct and balanced it'll run at 450rpm when you reset the stops so it does. When they are right, plug the wire back onto the cut-off valve.

Now set the idle circuit mixture and the overall speed with the stuff on top of the left carb. After than you should be able to disconnect either of the main cut-off valves (not the idle circuit one - the others) and the revs should drop equally.
That's just about all there is to it discounting the chokes. Have another go, I feel you'll get there and when you do it'll seem simple.

 

That's a great bit of Info mate. The idle circuit, with pipes joining the manifolds, is this the servo pipe? I only have pipes for the servo, joined together then tee off to servo, and the dizzy vac which is same setup. Am I missing one? Or is the servo vac the one you are talking about?

 

Outside of manifolds are the connections for balance pipe tee'd off to the servo.
Inside is the idle circuit - one pipe on each manifold and an extra one to the left hand carb to feed it via the speed and mixture screws on top.
What you mean dizzy vac is same setup? Dizzy vac = small pipe to nozzle on outside of left carb near the bottom and not connected to any other pipes.

 

I have thin 4mm servo vac pipes from both carbs to a central tee, then to dizzy.

 

Stupid complicated carbs at first glance, but quite simple when you break them down into chunks.

 

But there isn't a distributor vac port on the right carb. Piccy please. I suspect your plumbing is mucked up.

 

4mm? Should more like 2mm.