Rough idle

[coppercity]

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.

[Mike]

Check the carb mounting rubbers for splits on idle a gap would open up revving the gap is sucked shut

 

Mike

[Runtoeat]

Is the sync tube running from each carb and going thru the airbox in place with none of the holes in the tube exposed?

[coppercity]

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.

 

 

[Mike]

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

[Duane Jefts]

Waiting for the "end of the story".

[Ed Cesnalis]

Waiting for the "end of the story".

 

We'll have to get Roger's phone tapped

[Mike]

Any update ??

 

 

Mike

[coppercity]

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.

[coppercity]

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!