1971 mercury 650 not firing on #2 cylinder

[fullthrottle]

Hi there, i have a 1971 mercury 650 4cyl distributer ignition. I replaced the plugs, did compression test all were spot on, spark is good, checked all the fuel lines and the fuel filter, all seem fine. I tore everything apart thinking maybe the carbs were just gummed up, they looked great, cleaned them anyway, put everything back together and fired it up, ran the same. plugs were pretty oily, not a mixing issue because i thought that right away and filled a new tank and ran it, same thing happened. Also looked at the diaphram in the fuel pump and the check valves, looked allright, replaced all of them anyway. I finally went back to checking the spark again with a spark tester and it had great spark on all cylinders, let it ran and started pulling the plugs off one at a time and found out that the #2 cylinder did not change the idle, so im getting spark but it's not firing, but all the cylinders fire. anybody with any info on this would be greatly appreciated, thank you

also when i run it, it runs just fine no sputtering or coughing.

 

[FLATHEAD MAC]

Re: 1971 mercury 650 not firing on #2 cylinder

:facepalm: HAVE YOU CHECKED COMPRESSION. you got spark on #2 but no fire ? since changing fuel and all else, had running and pulled plug wire to no avail,
after the changes what does spark plug look like? also just a thought , possible bad sparkplug, check plug gap.

 

[Sunfish12]

Re: 1971 mercury 650 not firing on #2 cylinder

Swap spark plug wires and see if the no fire moves. Check inside cap for corrosion.

 

[Faztbullet]

Re: 1971 mercury 650 not firing on #2 cylinder

Compression or reed problem. Does it spit back or have a huffing noise out of #1 carb??