1988 40 hp yamaha 2 stroke bottom cylinder plug fouling

[w2much]

New to me engine. 3 cylinder 3 carbs.Oil injection.110 compression in each cylinder spark in each cylinder, Only running on two top cylinders. Bottom plug is wet and has spark. Looks to be oil fouled ,Need help here. Any suggestions., Could the primer be the issue? It is on the bottom carb.

 

[99yam40]

fuel pump leaking into crankcase would be my guess

 

[w2much]

I did a bone head . I ran premix, forgot about the oil injection. The fuel pump does sound like a possible culprit. She runs fine on the two top cylinders. Would the premix foul the plug or would it just smoke like crazy? I have run old outboards on 25 to 1 mixture. Cleaned the carbs and will fire it up later on with proper fuel.

 

[99yam40]

too much fuel will cause the cylinder to not burn the fuel properly.
just something to check on

 

[w2much]

All three plugs are firing with hot blue spark. Will jump from the inside of the boot to the plug easily. Problem remains bottom cylinder not igniting. Ran it without the fuel pump, just gravity fed the fuel. Compression is between 110 and 100 on all three cylinders.. Plug does not appear to have water on it. Cleaned out all three carbs.I am mifffed. Reed valves?

 

[w2much]

Fuel pump does not appear to be the problem. Switched coils just to reassure myself that the spark I was seeing was indeed hot enough. Idles great on top two cylinders. Will idle on any one carb. Could this be an internal powerpack issue? Could there be water in the cylinder(does not appear to be) even though the compression is at 105.? Top of piston is cleaner than the others.