SonexBuilders.net

Hi all,
My RPM gauge is showing 200rpm less and we have tuned on the carb and the engine is running smooth but still showing 200rpm less. I had flown to a local airport days about 13 miles away from my base the plane had set outside all day and my problems started on the flight back. I didn't notice any engine roughness and my airspeed seemed usual. The next day I started the plane and it was running rough at idle. when I went to pull the mixture to kill the engine it wouldn't die until I pulled it pretty hard to move it a final 1/8 to 1/4 inch which I had never done before. I pulled the cowl and didn't see anything wrong but I think it may be in the mixture arm or my cable. I tried to tighten the screw that holds the arm on but was tight. Any ideas what to check? Could my gauge be at fault? At this point I am thinking about putting on my Zenith carb I got with the motor. Thanks Densil

Check to see that the mixture cable hasn't moved in the mixture arm. Make sure the cable can move to cut off and open to at least 45 degrees. Also check that the carb needle hasn't turned rich. Both symptoms you describe could be due to being rich. Also does the rough idle reduce or go away if you lean it on the ground? I suggest re-tuning the carb per the published procedure before switching carbs.

Thanks Bill for the information. I will re check the mixture arm tonight. If you pull the mixture control back and the engine doesn't increase in RPM is that a sign of being to lean?
I have the older aerocarb maybe it is just wore out.

One more thing to check is the air filter. Make sure it is clean and oil free. Oil drops from the engine can really restrict the airflow of the filter making the engine run rich and reducing power output.

I mention this because of your relatively sudden onset of this low RPM condition as described in your initial post.

Thanks,

Jake

Update.
I had a friend hold a hand held RPM gauge and it is telling me that my RPM is off by 350. I had the RPMs set at 2000 and when he took the reading it showed 2350. He is thinking the problem could be with the fuse not making good contact. I plan on re running the wire and replacing the fuse. Has anyone ever had a RPM gauge go bad? I am using a Westech analog readout that hooks into the P lead.