Zenith carb problems.

[Tajman]

Having only run the engine for 5 minutes after rebuild, I was pleased it ran reasonably well. So I thought I would put the new fuel lines and filter in place. I passed the line from the tank (8mm i/d) through he bulkhead having removed the carb for better access. Filled up the filter with fuel and fitted the pipe to the pump and from pump up to the carb.
Turned the key and the engine fired up straight away but it was uneven,lumpy and struggled to run. Bit smokey as well. Not as smooth as the first time. I also noticed fuel around the base of the carb.
So I thought that maybe that I had done something to the carb whilst taking it off and back on again. So off with it again and onto the bench for a look and strip down. As it was a year since I last did that, I check out a couple of You tube videos for a bit of guidance. In one I noticed, although same carb but off a Porche, the brass fitting under the carb body, called the pump pressure valve, has a fitting within a fitting. this screws out seperatly from the bigger screw. In the video there was a small spring inside this. Not present in mine. See Photo. I had a small "blanking off" disc, just 2-3 mm diameter in the bottom. Anybody Know how its supposed to be? the Parts manual does not show anything. Item 103.
Anyway after that I found what I believe to be the problem. When tightening the nuts that bolt down the carb onto the manifold. (there are 12 mm spanner size, although the studs are M8) I had bent the brass idle adjusting screw. I'm sure that caused the engine to run roughly .
So I need to get a new one to be sure. anybody know of any suppliers? Initial web search was not very fruitful. I am suprised how many vehicles used this carb and it seems to have a good reputation, if you don't damage it!
One last question . In the middle of the air intake of the carb is a threaded pipe. I have no fitting to go in there. I presume it held something not Haflinger realted or am I missing something? See photo.

[heinkeljb]

I had a similar issue when I took my carb apart. There should be a thread detailing things. Not sure I remember exactly what was the issue and therefore the cure. As far as parts are concerned, there should be all the bits except maybe the jets in the correct sizes as you have rightly pointed out, they were fitted to a fair number of vehicles in the day. Some were very expensive so those owner are more prepared to pay for stuff to be re-made!
Anyway, the little Bakelite disc is a one way valve flap and should be in there. No spring in mine either. Likely for some other application - same with the threaded hole in the top - nothing in mine.
You should be able to get the brass adjuster from one of the Haflinger suppliers or from a company that specialises in early Porsche restorations. It also shouldn’t be that difficult to have one made if you can find someone who has a lathe.
These carbs are very prone to getting dirt in the jets, so good fuel filters and buy a can of compressed air to blow things clean. Much easier than trying to poke something down those small holes and much less likely to damage the jets.

John

[Tajman]

Thanks John, very helpful.
I managed to order the bits I needed from Classic Carbs UK. I have installed the original fuel filter with a new element.
I have found in the past with garden machinery maintainance and carb problems that aerosol carb cleaning spray is vary efficient. helps take off the old "varnish" that old fuel leaves and you can spray in the air intake whilst engine running briefly to ensure the cleaner goes through the system.
I also have a compressor for those cleaning jobs. I checked against the parts manual that I do have the correct jet sizes.

Jeff