1977 25HP Evinrude cutting out.

[James R]

Starts easily and runs for a short time in idle or at higher revs then "pflut" and stops. Restarts without any changes and does the same thing. Carb has been cleaned and rebuilt. Compressions at or near 120. New plugs. Sparks jump a good size gap using tester. Tried fuel pump by squeezing primer while running. No different. Resistance tests on stator show good. Haven't done a voltage test while running yet. Got a bit cold outside so that will have to wait.
Would appreciate any input on this. Maybe someone has had a similar experience.
Thanks.
Jim.

 

[flyingscott]

Sounds like a lean sneeze. Open the low speed screw another 1/4 turn

 

[racerone]

Agreed with above post.----Make sure throttle plate is opening at the correct time.----If it opens too early the motor will often stall.

 

[James R]

I thought a lean sneeze as well so I tried opening the Idle jet screw a bit at time until I had got to about 2.5. Smoked a bit more and I got more reside in the barrel but it still went pflut after a while, just as I thought I had it, and it cut out again.
I have the ignition advancing before the butterfly opening but I will examine the Sync again.

 

[racerone]

Have to ask.-----The high speed jet ( orifice plug ) is clean ?---An item found screwed into the bottom of the float bowl.

 

[James R]

Having mulled the issue over I am going to remove the carb again and go through the cleaning one more time. I could have missed something although I have done dozens of carbs in my time. I will let you know the results.
Thanks for your encouragement.

 

[kbait]

Faulty kill button can drive you nuts! Disconnect it and test.

 

[James R]

I will look at the kill circuit but at this time I have the following. I removed the carb and checked it, spotless. I re did the cleaning and reassembled. noted that the tubing which bleeds the lower cylinder to the intake manifold had seen better days so I replaced it. Ran the motor and adjusted the idle jet out to richen the mixture and it will run now without dying. However the upper cylinder is not working as hard as the lower cylinder. Pull the top plug wire and the motor changes but very little. Reconnect the upper and pull the lower plug wire and the motor stops. Does anyone have the resistance specs for these coils. They don't appear in the Evin' official manual or at least I haven't found the info.
I had a similar issue with another motor where one cylinder was not working well and it turned out to be a piece of acorn shell stuck in a reed. Visual check with a lamp through the hole shows nothing untoward.

 

[Crosbyman]

just measure both boots to frame and they should be similar.

swap the coils to see if the problem follows the coil or not.

 

[racerone]

Check the reed valves.