Continental O-300 Running Rough at Mid RPM

[hish747]

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

 

[Tom-D]

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

Tell me about changing the carb? new or rebuilt?

 

[hish747]

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

 

[Tom-D]

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

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?

 

[hish747]

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?

Intake hoses are in surprisingly good condition.

 

[GLDP]

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

 

[Tom-D]

Intake hoses are in surprisingly good condition.

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