ZZ Top Posted September 2, 2015 Report Share Posted September 2, 2015 My 2006 CTSW with 912ULS, 510 hours. Engine starts great, runs great, especially with the new soft start modules. Problem, after take off, climbing to altitude, going to cruise all is well. When I throttle down to about 4500 RPMS the engine runs very very rough, almost to the point that it seems to be starving for fuel. If I go back to full power the engine will smooth out and run well. Lower the RPMS to 4100 engine runs good. Have the carbs rebuilt and balanced. Any ideas? Thank you in advance for your input. Link to comment Share on other sites More sharing options...
Tom Baker Posted September 2, 2015 Report Share Posted September 2, 2015 Check the little clear lines that go from the carbs through the airbox. One could be disconnected or the line passing through the airbox may be pulled to one side exposing a hole in the line. If everything checks out there pull the intake hoses off the back of the carbs and reach into the carb and check to make sure the slide is moving freely. Link to comment Share on other sites More sharing options...
ZZ Top Posted September 2, 2015 Author Report Share Posted September 2, 2015 Thank you Tom. Did check the line through the air box, connected. If the slide is not moving freely, why would this happen only midrange between four and 5 K? Plus this does not happen all of the time and at times much more severe than others. Did check the carb bowls for contamination, clean. Link to comment Share on other sites More sharing options...
Tom Baker Posted September 2, 2015 Report Share Posted September 2, 2015 On the line for the airbox you also need to check that the hard plastic tube has not slid to one side exposing the holes that are cut into it. On the slides when you change throttle settings the diaphragm moves the piston up and down controlling air and fuel mixture. If one is hanging up as you reduce throttle it will create a big imbalance between the carbs. I have seen both of these issues cause the problem you are describing. Link to comment Share on other sites More sharing options...
C ICEY Posted September 2, 2015 Report Share Posted September 2, 2015 Check your gearbox; Friction torque and potential repack. Often manifests as rough running in that range, especially if you use leaded avgas. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 2, 2015 Report Share Posted September 2, 2015 I think this is an easy one, but you won't know until you look. Most likely the carb vent tubes that go through the airbox. Pop the top cowl and look at the carb vent tubes that go through the airbox. My bet is one has pulled out of the other tube or the tube through the airbox has been pulled too fat out the side of the airbox and has exposed one of the three holes in that tube. Just pull the white tube and exposed hole back into the airbox. The carbs have vent tubes that come off the sides. These tubes must get the same air pressure or the carbs become very unbalanced. Some planes have the tubes short and just tucked into the bale along side the carb bowl. Some have the Rotax airbox that these tubes connect to. Some like the earlier CT's have these tubes connected and then run into the airbox. You just don't want these tubes in any high or low pressure areas and want the pressures on both carbs fairly equal. Failing to do this changes the float operation due to pressure changes within the carb bowl. Link to comment Share on other sites More sharing options...
ZZ Top Posted September 2, 2015 Author Report Share Posted September 2, 2015 Thank you to all, will be going to airport this evening to fly. Will check this out then. It is remarkable how well the engine runs with the new modules. Starts immediately. The seat belts are still a pain the behind. Have tried some of your suggestions. Still not a happy camper. Link to comment Share on other sites More sharing options...
procharger Posted September 4, 2015 Report Share Posted September 4, 2015 Whats wrong with seat belts? Link to comment Share on other sites More sharing options...
CT4ME Posted September 5, 2015 Report Share Posted September 5, 2015 Some folks don't like the fact that the seat belts may auto-loosen over time, and may have a tendency to fall off the shoulders... Link to comment Share on other sites More sharing options...
procharger Posted September 7, 2015 Report Share Posted September 7, 2015 I bought 8 seat belt clips like you use on baby car seats to keep belts from moving, they will not slip any more. E bay nice chrome ones look good in plane. Link to comment Share on other sites More sharing options...
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