1998 90 hp yamaha fouling plugs and oil in carb throats

[ssoileau]

My 90 hp yamaha 2 stroke ( C90TLRW) ran perfect until afew months ago. It started fouling all 3 plugs then eventually wouldn't start. I had to flip the enrichment valve on the miidle carb to off to start each time. I changed the plugs, fuel filter and removed, cleaned all 3 carbs and ran seafoam thru the fuel system. Did all this twice. It ran perfect for 3 or 4 hrs then back to the same problem. Each time I cleaned the carbs I noticed oil 2 cycle oil in the carb throats and carb cover. Mixing oil/fuel at 50/1 and the gas does not sit very long, I run it often. It does run fine at high speed and we ski often. The compression seems fine.

 

[rodbolt]

Re: 1998 90 hp yamaha fouling plugs and oil in carb throats

did you check the enrichment pump diaphram?
did you check the fuel pump diaphram?
that oil/fuel mix is what your seeing due to a flooding condition.
when you turn the valve to off you shut off fuel to the enrichment system.

 

[ssoileau]

Re: 1998 90 hp yamaha fouling plugs and oil in carb throats

I ordered a fuel pump. I did take a look at the enrichment valve. Really don't know what I'm looking at but seems OK. I thought about changing it but it's kind of expensive when I'm not sure if its good or bad.

 

[rodbolt]

Re: 1998 90 hp yamaha fouling plugs and oil in carb throats

not the valve.
the pump that operates the system.
its located under the cover that has the manual valve.
thats why it has a manual shut off. just incase the diaphram fail.
its also not the engine fuel pump.