2000 GasGas EC 250 Fouling Plugs with Transmission Oil

[disco1994]

I'm working on what I think is a 2000 GasGas EC250. The title lists it as such, but the vin and engine serial number look more like they could be for a 200cc.

I have limited history on this bike. It was running good for about a month until two weeks ago. Now it fouls the plug with what seems to be transmission oil and stalls within about 10 seconds of idling. Quicker if you try to pull the throttle. Compression is about 145psi. Reed valves look to be newer carbon fiber and in good shape. Exhaust collector had a couple tablespoons of oil in the bottom. Silencer doesn't show any evidence of needing repacked, but it's sealed with rivets.

Air filter looks clean and newly oiled. Carburetor seems to be surprisingly clean and well adjusted. Elevation is about 650' near Detroit here. Pilot jet 42, main 178, needle set as low in the jet as possible (slot 5?). Has 40:1 93/syn fuel/oil in the tank. Tried also with 93/semi syn 40:1 and with 93/semi syn 80:1 with no change. Also tried running the bike with the airbox detached.

Spark plug seems to be doing its job, though I tried another plug and also watched an inline spark checker too.

Drained out the transmission fluid and started the bike and it seemed to operate normally. Just like new.

Pulled the clutch case and looked at the RH crank seal. Visual inspection looked fine. Removed the seal and it tore. It's a little old and brittle feeling, but it didn't look terrible. I've seen much worse. Looks like an original 30-52-8 double lip oil seal. Couldn't find a direct replacement locally.

The local bearing store had an SKF 30-52-7 single lip seal. I threw that in the bike to try it and it still seems to have the same problem. Ordered OE GG part and it should be here some time?

I might just be posting to hear myself talk. I'll try to post again when the right part comes in, but for now the bike is still acting up. Going to pull the crank case drain later and see if anything comes out.