Zenith carb problems.
Posted: Sat Jan 30, 2021 7:14 pm
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.
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.