Gasgas ec300 2006 crank shaft seal help

[dopeman264]

Hi everyone

Ok so I recently bought a 2006 ec 300 the bike did run relatively good, so after a few rides I decided to change the oil, when I drained it only 600ml
Came out so i replaced it with 900ml and it started smoking really bad and burning oil.

I?m guessing the crank seal was already blown and 600ml
Sat below the seal.

After stripping the bike I noticed the seal looked like it had popped out (see pic)

So ordered some new seals and o-ring and installed them as per workshop manual I used fresh 900ml of oil again.

The bike ran great for a couple of hours then started smoking really bad and burning oil.

After stripping it down again it appears the new seal has also popped out, has anyone seen this before or have any idea of what?s happening please

Tia steve

[(F5)]

Ok that's weird.

Erm there should be a dirty big vent to stop pressure build up. Is that clear,,? Just trying to remember on the gasser where it is. Too many motors in my head.
Edit forget that, late in day. Wrong way. Um. Did crank bearing look ok? Was seal loose to get in?

A leak down test should only be done at a few psi, so I wouldn't expect primary compression to exceed that. Might be a good test of new rebuild. Maybe seals were made a bit small vs another brand?

[dopeman264]

Hi

Thanks for the reply. Seals was tight there was a grove in the bushing but seal didn’t sit on this so I cant see that being an issue, bearing was good and didn’t see any play in the crank.

Iv now turned the bushing down 2mm as couldn’t find a replacement and fitted a 36.52.8 from a ktm.

Hopefully this will fix my issue I will find out today.

[Neil E.]

Sounds like you had excess pressure in the crankcase. I don't know how it could get high enough to push out a crank seal.

[Moto7man]

I did find this thread.


http://www.gasgasrider.org/forum/showthread.php?t=5361

[dopeman264]

So i did sort the problem out turns out the wood ruff key was damaged on the fly wheel side and was causing bad timing that was causing it to back fire and in turn blow the seals out

all repaired now and running as it should


thanks all

[Moto7man]

Good job

[(F5)]

Ha!

Ok that's not what I was thinking. Good catch.