Help - bad running and knocking all of a sudden

[MagicWagon]

My 81 2.0 Air cooled has been running well since I got it, but I drove it to work tonight and things are not well. I'm worried about driving it home in the morning and would welcome any advice.
It sounded like it was missing. It ran ran OK with virtually no accelerator but even a small amount of pedal and it sounded like missing/popping/kind of hollow sound like a moped. Was only managing 40 up hill.
When I came off the motorway it stalled at the lights and would not run without the accelerator down.
Most worrying, when I pulled up at work, I restarted it to have a good listen and there is a loud intermittent, irregular knocking, and when it knocks, I can feel it through the depressed clutch pedal.
Unfortunately I have no tools in the van so I can't do much here. Is there anything obvious I can check that could cause these symptoms, than might persuade me it is OK to drive it home ?

[sarran1955]

Hello,

2 suggestions..

1 check that all the spark plugs are in tight..

2 look for a rubber hose come loose , either off the distributor, or maybe the feed off to the left (to the brake servo)

Aircooled Bliss..

Cordialement,

[MagicWagon]

I checked the spark plugs are in tight, and can find no rubber hose loose from distributor or carbs/servo etc.
Now it's cooled a little, the knocking seems to have gone, but still wont idle without accelerator pressed. Is that bad news if the knocking comes when it is hot ?

If I jam the linkage to get it to run at low speed, there is considerable rocking of the engine from side to side.
I tried taking each plug lead off at the distributor one at a time, and all seem to make running slightly worse, so not as if it's running on three. There is a strong spark at each plug lead as I go to reattach each one.
Stuck for ideas with no tools and not sure if it's risky driving it home (about 15 miles).

[captain Byrne]

What state are the plugs in? Should all be the same colour - light brownish.

[MagicWagon]

I called out recovery in the end, and for the first time in my life, they actually found the fault.
There was a hole in the carburettor ! - will post pics later and hopefully someone can help explain it.

[captain Byrne]

Glad it's not anything more serious!

[MagicWagon]

So, what the recovery guy found was that there was a hole in the carb, at the rear of the left hand carb, in the part of the carb where a hose attaches leading to what I think is the bypass cutoff valve. I then found that there was a small (approx 1cm) blanking plug which had come out which I retrieved. He then pushed it back in and cable tied a cut bit of hose pipe over it to stop it coming out again. If you look at the attached picture you will see the bit of yellow hose held on with a blue cable tie.

What I am wondering is
- What is this hole/blanking plate for ?
- Should I stick something like araldite over it to stop it coming out again ?
I assume the engine was shaking so much with misfiring that it caused the knocking I could hear and feel through the clutch pedal.

[MagicWagon]

Here's a picture I found online showing a similar carb. I've added a red arrow showing the location of the metal disc that came out. Any ideas what it's for/what I should do ?

[captain Byrne]

Looks like an expansion plug. If you can get in, give it a tap in the middle with a punch to spread it out. Maybe use some decent sealant or a little araldite.

[sarran1955]

Hello,

Yes , I've found these plastered over in the past..

I keep a tool roll, together with a telescoping wheel brace in the spare battery case.

I'll have to make a list, but it will get you out of trouble and takes little space, without rattling..

I also carry a sandwich box with fan belt, plugs, points and condenser (yeah really ),rocker box gaskets and spare bulbs.


If the engine was really rocking badly, you might want to check the engine mount rubbers under the fan housing have not separated .


Aircooled Bliss...

Cordialement,