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.

 

[Gasser Nate]

There is also an o ring under the collar. You should replace that as well. Hopefully the crankcase gasket isn?t split between the engine and gearbox. That will be a full motor split.
You should look at the numbers on the needle and have a read through the thousands of jetting threads on here. If it is the stock N1ef needle throw it in the bin and source another different needle. NEDW works well as well as the N3EW series.

 

[Zman]

Did the single lip seal work?

 

[fred99999au]

Which way did you face the lip to seal? Pressure in the crankcase or vacuum?

 

[disco1994]

Solved!

The important bit: SOLVED. Installed bolt into open threads in top right side of jug above power valve bearing.

I worked on this intermittently over the last couple months because I've been busy with many other projects. I got pretty well acquainted with the bike. The exhaust has been off and cleaned out. Its an aftermarket FMF full exhaust that could fit better. The power valve looks to be in good shape and moves properly. The area around the left side power valve bearing was full up to the bearing with oil/fuel--not sure if this is normal or if the bike was just loaded up from cold running. Second compression test came to 155psi--any data points for compression with a new top end? The right crankshaft seal did not work with a single lip seal--it was much worse. The seal that I removed from the bike was a generic SKF seal. I was able to track down and install a gasgas original seal and install it with the flat side to the trans oil. The SKF double lip seals I found on amazon.com would have probably done the trick. I could not find any indication that there is an o-ring around the crankshaft on this year. I've seen pictures of slightly newer bikes with that o-ring, but it looks different on this crank and I don't know if theres an o-ring hidden in there or not. If there is another collar that comes off the crank then the crank would need to come out of the bike and use a bearing separator to remove that collar.
The carbon fiber reed valves look nearly new like many things on this bike. I'm told that these came stock with carbon fiber reed valves but I don't have proof of that. I installed a new replacement carburetor (knock off from eBay $40 new) and used the jets/needle that came in the bike. I couldn't see any markings on the needle so I'm assuming it's stock. It hits pretty good, but I'll probably still look into that recommended replacement needle. New NGK spark plug went in just because. Checked and rechecked each part of the charging/ignition system and pinned out the wiring. Was getting ready to pull the top end and overhaul just to open her up and see the insides but knocked down a few last doors beforehand.
Removed the fuel tank and shook out all the old fuel mix and replaced with my trusted blend of 1:40 Lucas semi-syn and 93oct.

While I had the tank off I got a good look at the open threads just down to the right of the cylinder head. This is a threaded hole that goes to the area around the right-side power valve bearing. I don't see any logical reason for that to be plugged for the bike to run happy but I guess it needs to be. Any pictures/info I could find on the line shows just a little shiny nipple sticking out of those threads. Looks like an aluminum barb fitting from what I saw. Even read somewhere that it might be a crankcase vent? In any case, I installed a m6x1.0x10mm bolt in that hole and she lives! Whatever was in that hole before must have rattled out while riding and so the whole time I was just plain missing something. Have had three successful riding/tuning sessions with the bike thus far and it seems quite happy. Hopefully its all just routine maintenance and care from here on out

 

[Gasser Nate]

That is the crankcase breather and it most definitely needs to be vented to the atmosphere. It should not make any difference whatsoever to the running of the bike unless you have a major crankcase leak. I would still be leak testing that bottom end