#3 cylinder rough & white smoke

[anthonybradley]

Hi, have an early - mid 80s Yamaha 40 autolube (3cyl 2 strioke), was serviced start of year, and been running fine, but now running rough / stalling at idle etc.

Long story short it will run ok just cyl 1 or just cyl 2, but on just cyl 3 it splutters and stalls, and produces white smoke, all 3 cylinders together it runs a bit better but still rough and some white smoke, so def seems to be cyl 3 at fault. Done a compresion check and all ok, cleaned / swapped plugs and checked spark etc. Have stripped #3 carb and cleaned it, but it didnt really seem to need cleaning anyway and fault still the same. Fuel seems to be getting into cylinder as plug is wet if disconnected. All linkages are free and easy, and not been moved since last working ok.

Any ideas? I suspected head gasket, but compression check is ok. Checked fuel pump and supply but they must be ok anyway as other cylinders run ok.

Anys and all ideas welcome

Thanks Anthony

 

[anthonybradley]

Re: #3 cylinder rough & white smoke

oh also meant to say:

1) it runs better for the first 10-15secs (although still not great if #3 is live). Is there some system in the CDI that does something different / extra upon startup?

2) whats the alloy assembly on the port side of #3 carb; has 2 wires coming from it and a pipe, and is bolted to the float chamber, with a hole allowing fuel to flow into / from the chamber? I can only presume it is some type of enricher?

Thanks Anthony