Continental O-300 Running Rough at Mid RPM

Discussion in 'Maintenance Bay' started by hish747, Oct 21, 2020.

  1. hish747

    hish747 Pre-takeoff checklist

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    Hi Guys,
    I'm in the process of restoring a Cessna 172 with a 1300 hour Continental O-300D. This plane has sat outside for about 6 years. We rebuilt the fuel lines and changed the carb, all new spark plugs, adjusted mag timing. The engine starts and runs well enough but is rough at the mid rpms. Any shots in the dark as to what might cause this?
    Thanks,
    Hish
     
    Last edited: Oct 21, 2020
  2. Tom-D

    Tom-D Taxi to Parking

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    Tell me about changing the carb? new or rebuilt?
     
  3. hish747

    hish747 Pre-takeoff checklist

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    I purchased an overhauled Marvel-Schebler MA-3SPA carb from Aircraft Spruce. Are these known to have issues?
     
  4. Tom-D

    Tom-D Taxi to Parking

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    They are supplied by Kelly, I don't know of any problems

    sat outside for 6 years, I don't know where to start, How are the intake Hoses?
     
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  5. hish747

    hish747 Pre-takeoff checklist

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    Intake hoses are in surprisingly good condition.
     
  6. GLDP

    GLDP Pre-Flight

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    Check to see if any of your engine mount bolts are loose - engine to mount and mount to firewall.
     
  7. Tom-D

    Tom-D Taxi to Parking

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    Have you sniff tested the engine ?
    disconnect the Primer line at the "Y" pipe under the left intake
    see that changes things.