carb problems

[mtnguy2019]

I have an 84 70 hp Evinrude motor. I have just rebuilt the carbs and have a cylinder misfire issue. while idling the center cylinder is not firing. I have pulled the plug wires while it is running. it has plenty of hot spark. I pulled the center carb and swapped it with the top carb. the center carb makes the top cylinder not fire. and the center which has the top carb does fire. I could only try it at idle since the linkage wont hook up that way. I have been back through every inch of the center carb a couple more times. everthing looks good and all ports are flowing. any idea, thanks Frank​

 

[joereeves]

The small brass tube that is off center within the high speed nozzle is no doubt plugged.

Clean it thoroughly with a small diameter piece of single wire steel, then blow it out with pressurized air.

 

[mtnguy2019]

The small brass tube that is off center within the high speed nozzle is no doubt plugged.

Clean it thoroughly with a small diameter piece of single wire steel, then blow it out with pressurized air.

That was the problem. Even though I had blown air through the tube previously. It did take a stiff wire to fully open the passageway. Thanks for your help.

 

[timguy]

Way to go Joe. Mtnguy good job. Physically cleaning parts inside and out is critical with these carbs. So many people use carb spray and air pressure with a little poking and scraping, but that doesn't always work. Tubes, jets, etc., have to be physically opened to correct size, which sometimes means removing cap/welch plugs as well.

 

[mtnguy2019]

Way to go Joe. Mtnguy good job. Physically cleaning parts inside and out is critical with these carbs. So many people use carb spray and air pressure with a little poking and scraping, but that doesn't always work. Tubes, jets, etc., have to be physically opened to correct size, which sometimes means removing cap/welch plugs as well.

I did pull the Welch plugs so I could see the wire pass all the way through. Great forum.