Gasgas ec300 Crankcase pressure problem

[Stijn_M]

Hello!

Some time ago I bought myself an old ec300 (partly 2000 /2006 model) wich had been resting a couple of years beneath a tree. After some weeks of work and lots of new parts, i recently got to starting it up. It started but would not idle or run decent (giving a very rich impression)... After experimenting with different jets, needle and floathights i still had no succes...
Now untill i drained the crankcase, there was nothing in there but still i cranked the engine and suddenly the damn thing starts and revs like a rocket but only without the crankcase bolt?! As soon as i hold my tumb over the crankcase-hole the engine stalls... Anyone have an id where i need to go look to find its problem? Could it be a timing problem that i need to lift the cilinder? I am using the middle base gasket.
Right now i'm starting to remove the cilinder again to make sure i have no blow by on the piston. But that would seem odd to me since the piston looked very well when i rebuild the engine and it has a good compression.


Kind regard
Stijn

[Stijn_M]

I seem to have found the problem, the bolt of the powervalve came off... I feel like such a dickhead now

Edit: this was not the cause of the problem... After installing everything it still wont run idle with the bolt in the crankcase.
- it does run without the exhaust, i am using a doma racing exhaust -no restrictions-. Could it be that i used to much glassfiber in the muffler?
I understand that this could give some performance differance but that this would make the bike run or not is a bit hard to believe in my opinion...
Edit: even with the banana -no muffler- it wil not idle

[dANbOT]

With the crank drain bolt out, your adding a large source of extra air, and undoubtedly leaning out the mixture. This points to a rich condition as you mentioned.
As long as the silencer packing is not blocking the flow by being installed incorrectly.... being packed too loose, or too tight wouldn't stop the bike from running reasonably well.
-was the carb thoroughly cleaned out?
-float level checked?
-float is functioning correctly?
-reeds are in good shape, and sealing?

A carb that as sat for years is likely to be full of hard to clean residue, unless prepped for storage meticulously. There is a good chance that the idle air passage is blocked, or the choke circuit could be leaking excess fuel into the engine.

Out of curiosity, what are your carb settings? elevation?

[Stijn_M]

The exhaust is not blocked by any way, the carb, i cleaned ultrasone and several times i made sure all passages in the carb are open, the floats still float, it has a new floatneedle wich closes... And the height is set to be parallel with the bowl prox 16-17mm, just enough not to droole while on the sidestand. The carbon boyesen reeds looked fine to me so i did not change them. I am using a 172mj 35pj N1EF needle (all new) even tryed with 42pj and 140mj all had the same problem... The elavation is 25m above sealevel.
Tommorow i will try to borrow a friends vforce reedvalve and his carb to check if i can resolve the problem if that doesnt solve things i will be looking in to a new piston probably...

[dANbOT]

Sounds like you've covered most of the likely suspects, and your jetting certainly does not sound overly rich for your elev. I run a 35 pilot @ 3000 - 8000 feet.

-Not sure if I would bother swapping reeds, so long as yours appear to be sealing well.
-The carb swap may show there is a fault, or blockage remaining in yours so I agree that its a good test if you have a compatible, and known working unit.
-Low compression does usually exhibit rich conditions, so the piston is a possibility..... but it would have to be in pretty rough shape, or have rings stuck compressed in the grooves.
-Also a shot in the dark, but maybe its ingesting trans fluid, or coolant?

In your position, I would be inclined to do a compression test, and leakdown test to verify the basic health of the engine.

[Stijn_M]

Regarding the reeds: Since the engine doesn't extrude fuel/air through the carb and that they look reasonebly well i will not bother to change them. Danbot, as you asked, i do not think any of the seals are leaking. It does not appear to loose transmission oil or coolant and nothing comes out of the crankcase venting except for some smoke and blackish-too-rich-looking-dripping. Tommorow when i can experiment with the other carb (wich works fine on the other ec 300) i hope to have some closure on where the problem could be... If the carb does not solve it i will try to do a press test. But still like you say, the piston would need to be in a pretty rough state to halt the engine from a decent performance left at all from stalling like mine does... I did not bother to measure the piston and segments since they looked pretty well after cleaning when i rebuild the engine.
Either way thank you very much for thinking about it and trying to resolve my problem!

Kind regard
Stijn

[Jakobi]

What clip position is the needle in? What number slide? Once running with the crank case bolt out can you slowly close it and get it to keep running with the throttle part open?

[Stijn_M]

At the moment i have the needleclip in the top groove and i use the stock slide #7. I am able to keep the bike running with a min of 1/4-1/3 throttle open with a closed carter and exhaust installed. But the engine sounds very flat then and revs poorly.

[Jakobi]

Haven't left any rags stuffed in the airboot?

[Zman]

Verify your carb vents are not plugged with mud, bugs or golf tees (from riding on local golf courses).