Rough at 800 to 1500 rpm

[lbell]

My engine started running rough. Doesn’t seem to be a misfire. EGT at 1500 780 to 800 degrees in 1-2-3 400 degrees on cyl 4. EGT’s even out at higher rpm. No intake leak and good compression. I’m lost. Could there be something with the carburetor?

[Bill Tew]

My engine started running rough. Doesn’t seem to be a misfire. EGT at 1500 780 to 800 degrees in 1-2-3 400 degrees on cyl 4. EGT’s even out at higher rpm. No intake leak and good compression. I’m lost. Could there be something with the carburetor?

I had a similar experience a year ago. Cause was the primer leaking fuel into #4 cylinder even when fully closed. Disconnecting the primer line at the cylinder head and plugging the hole solved the problem. Have never needed the primer since.

Bill

[lbell]

I had a similar experience a year ago. Cause was the primer leaking fuel into #4 cylinder even when fully closed. Disconnecting the primer line at the cylinder head and plugging the hole solved the problem. Have never needed the primer since.

Bill

Thanks. Ill unhook it and see. I needed the primer once in Gallup NM when it was really cold. It didn’t work. I took it out and freed up the ball check. Haven’t needed it since.

[Dan L]

If this is an O-340 and if you’re nearing or over 500 hours it may be the spark plug leads. Sounds similar to my engine when I had around 600 hours. It is recommended to change them at 500. They’re about $20 each from Lightspeed. You need 8. The leads from the boxes to the coils do not need to be changed.

[lbell]

If this is an O-340 and if you’re nearing or over 500 hours it may be the spark plug leads. Sounds similar to my engine when I had around 600 hours. It is recommended to change them at 500. They’re about $20 each from Lightspeed. You need 8. The leads from the boxes to the coils do not need to be changed.

CC recommends 3 years or 500 hours. I can buy the 500 hrs but three years seems a stretch. Wires are MSD. A universal MSD 31229 set runs $116. Good pair if crimpers about $30. Also a better fit.

[Pete D]

CC recommends 3 years or 500 hours. I can buy the 500 hrs but three years seems a stretch. Wires are MSD. A universal MSD 31229 set runs $116. Good pair if crimpers about $30. Also a better fit.

Lightspeed initially recommended three years and 500 hours, has now been increased to 10 years or 500 hours. The CC recommendation follows Lightspeeds intervals.

[lbell]

I had a similar experience a year ago. Cause was the primer leaking fuel into #4 cylinder even when fully closed. Disconnecting the primer line at the cylinder head and plugging the hole solved the problem. Have never needed the primer since.

Bill

That did it. Was the primer.