coppercity Posted September 17, 2013 Report Share Posted September 17, 2013 Yesterday after a flight with a student we were idling at 1900 prior to shutdown when the engine began to lose rpm and run rough. I throttled it up just to troubleshoot some and it ran smooth above 2400rpm. Throttled back to idle and after a 30secs or so it started losing rpm and running rough again. During this time the right side EGT dropped off drastically. My first thought was a stuck or sunk float, so I pulled both bowls and floats are floating fine. Checked the settings on the idle mixture, both fine. Removed the idle needle on both to check for debris, none found in there or the float bowls. I have now removed the right carb completely and inspected it, no signs of debris anywhere or anything obvious. The viton tip on the float valve shows slight wear on the tip, could this be allowing enough fuel to bypass the valve and flood the carb at idle? Looking for any ideas. Thanks in advance. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 17, 2013 Report Share Posted September 17, 2013 Hi Eric, Put the carbs on the sync gauges so you can diagnose the problem. If you have one pulling more than 15" vacuum i.e. 20+ and the other is around 13-15 " then pull the one with the high vacuum and strip it. Flush with spray carb cleaner every orifice and follow that with high pressure air. Target the idle jet and small holes. Pulling the bowl won't find your problem because you are in the idle rpm range and debris very small. Once you got up to higher rpms the idle jet wasn't much into play and the main jet was just starting to take over. Only tiny debris gets clogged in the idle jet because small stuff just goes through the larger main jet. An air leak can also mimic this, but most likely not the problem. Just had one the other day. Wide spread in the needles on the sync gauges. Pulled and stripped the high vacuum carb and did the carb sync and it was back to normal. Link to comment Share on other sites More sharing options...
Mike Posted September 17, 2013 Report Share Posted September 17, 2013 Check the carb mounting rubbers for splits on idle a gap would open up revving the gap is sucked shut Mike Link to comment Share on other sites More sharing options...
Runtoeat Posted September 17, 2013 Report Share Posted September 17, 2013 Is the sync tube running from each carb and going thru the airbox in place with none of the holes in the tube exposed? Link to comment Share on other sites More sharing options...
coppercity Posted September 17, 2013 Author Report Share Posted September 17, 2013 Roger, I did have my sync gauge hooked up yesterday during troubleshooting and did not see any significant imbalance while it was idling rough. Mike, I will give the mounts a good look. Dick, This is on a CTLS with the Rotax air box, but I did check the sync lines going to each carb and they seem fine and were connected. Link to comment Share on other sites More sharing options...
Mike Posted September 17, 2013 Report Share Posted September 17, 2013 I had one last year as soon as it went to idle it run rough and stopped but if the engine was revving it was running normal the split on one rubber was right inside in the crease and under the clamp so couldn't see it till i took it off Mike Link to comment Share on other sites More sharing options...
Roger Lee Posted September 17, 2013 Report Share Posted September 17, 2013 Hi Eric, This is going to be a long detailed conversation and my fingers are already getting shorter. Give me a call. Link to comment Share on other sites More sharing options...
Duane Jefts Posted September 17, 2013 Report Share Posted September 17, 2013 Waiting for the "end of the story". Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 17, 2013 Report Share Posted September 17, 2013 Waiting for the "end of the story". We'll have to get Roger's phone tapped Link to comment Share on other sites More sharing options...
Mike Posted September 20, 2013 Report Share Posted September 20, 2013 Any update ?? Mike Link to comment Share on other sites More sharing options...
coppercity Posted September 20, 2013 Author Report Share Posted September 20, 2013 Engine is running well again. Here are all the things I did. Initially I thought the problem was in the right side carb as the plugs on that side were all dark and seemed as if the right side carb was flooding. I pulled that carb, replaced the floats, totally disassembled it and cleaned everything. Put it all back together, synced it up but still had the issue. Next I thought ignition so I replaced all the plugs checked all the connections to the modules. Still had the problem and ignition checks were always good at 70-80 rpm drop at various power settings from 4000 down to idle. After talking to Roger for awhile we decided a compression check was a good idea, did that and all was good. Roger suggested checking the float levels again so I did that. The left side carb was about 1.5mm out of whack. I reset that, disassembled and cleaned up the left carb, put it all back together and synced it all up again. So far everything is back to normal. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 20, 2013 Report Share Posted September 20, 2013 Hi Eric, Glad it worked out. I hate chasing ghost problems. I hear you're going to have another CT transition pilot there next week or so. Steve from my neck of the woods. I talked to him this morning. He is looking forward to coming down. Link to comment Share on other sites More sharing options...
coppercity Posted September 21, 2013 Author Report Share Posted September 21, 2013 Hi Roger, I wish I could have found the smoking gun to know for sure it was fixed. Yes, Steve will be down to see us soon. I hope he likes the CT so you can add another to your CT airforce up there! Link to comment Share on other sites More sharing options...
Roger Lee Posted September 21, 2013 Report Share Posted September 21, 2013 Hi Eric, That's the problem with cleaning or working over the carbs, they use smokeless powder. (No smoking gun) Link to comment Share on other sites More sharing options...
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