rough 912l on idle circuit
in 912 / 914 Technical Questions
8 years ago
Hello Group, Rob, Roger et al'
I need some fresh ideas on this. My 912ul will idle OK at 1800 rpm, it will run fine above 3000rpm but between 1800 and 3000 it runs rough, like a VW kind of rough. Here is what I've done so far to try and solve this, had the carbs rebuilt, had the gearbox rebuilt, new plugs, plug caps and ing. wires (rpm drop same on both ing. boxes) new carb sockets, weighed the new carb floats,checked the float arms,made sure the enrichers were coming fully off and correctly installed, synced the carbs over and over, sprayed starter fluid looking for air leaks, cleaned the idle jet over and over using cleaner, air, ran a little wire through the openings. Nothing I've tried made a bit of difference until I turned the idle mixture screws down to about 1/2 turn out instead of the factory recommended 11/2 turns. It runs much better with the mixture screws turned this far in but still not as it should. Something has to be out to required this kind of adjustment ? I can turn the fuel off as it is running rough at 2500 rpm and as is starts to run out of fuel is will pick up a 100 rpm or so and run smooth as can be for a few seconds just before it quits. I was thinking it had to be a air leak somewhere was making it run lean but I can't find anything and why would leaning out the idle mixture screws make it run better? All along it has run fine above 3000 rpm. Anybody want to take a shot at this one, like I said I'm out of ideas.
Thanks
EG
I need some fresh ideas on this. My 912ul will idle OK at 1800 rpm, it will run fine above 3000rpm but between 1800 and 3000 it runs rough, like a VW kind of rough. Here is what I've done so far to try and solve this, had the carbs rebuilt, had the gearbox rebuilt, new plugs, plug caps and ing. wires (rpm drop same on both ing. boxes) new carb sockets, weighed the new carb floats,checked the float arms,made sure the enrichers were coming fully off and correctly installed, synced the carbs over and over, sprayed starter fluid looking for air leaks, cleaned the idle jet over and over using cleaner, air, ran a little wire through the openings. Nothing I've tried made a bit of difference until I turned the idle mixture screws down to about 1/2 turn out instead of the factory recommended 11/2 turns. It runs much better with the mixture screws turned this far in but still not as it should. Something has to be out to required this kind of adjustment ? I can turn the fuel off as it is running rough at 2500 rpm and as is starts to run out of fuel is will pick up a 100 rpm or so and run smooth as can be for a few seconds just before it quits. I was thinking it had to be a air leak somewhere was making it run lean but I can't find anything and why would leaning out the idle mixture screws make it run better? All along it has run fine above 3000 rpm. Anybody want to take a shot at this one, like I said I'm out of ideas.
Thanks
EG
