Gear Shaft seal blow-out

[Shorty_925]

Ive had yet another seal blow on the gear shaft of my YZF450('07 model). The seal is the one behind the sprocket, and behind the cover that stops the seal completely blowing off.

Ive replaced it once myself no worries, two or three rides later it blew again. So took it to a shop to get it done properly.

Got it back and did another two rides/races, and just over the weekend I checked it to make sure nothing was leaking, and sure enough it was a slow leak.

Anyone got an suggestions as to what is going on or I could possibly do differently to get this working right? Has this happened to anyone else? Is it common? Is it worth it to replace all seals along this shaft?

Would a blocked/covered breather pipe blow this seal? As I use a red bull can for the breather, so wondering if its blocking it up to much.

I have asked the local shops and they all seem surprised that its happened so often. I use my bike for motarding, so I keep a close eye on it as its happened once where oil pumped out onto the back tyre without me knowing and before I could blink I was on my backside.

[barty5]

sounds like the shaft has worn or there is damage to the casing is the leak form the inner part of the seal or form the outside edge?? it could be possible for a blocked breather to blow the seal with extra crankcase pressure.

[Shorty_925]

Yea I suggested that to the shops as well(about the blocked breather) and didnt really think it was that. They thought maybe the seals in behind the seal ive replaced could be worn. Havent had a chance to take a look at it as yet, hopefully tonight and have a look. Just wondering if anyone else has had this experience.

[WRock]

On the shaft there is a small o-ring, then a collar is pushed onto the shaft firmly over the o ring,which means the shaft o ring and collar all spin. The seal is fitted between the collar and housing. The seal normally wears grooves in the collar so it must be replaced as well. For the small cost the o ring should be done as well. The seal must sit on the collar in the right place and if pushed in too far goes past the bevel on the collar. The seal should sit only just flush with the housing.

[barty5]

as shown in part 28 29 and 30

[That Guy]

You've probably thought of this but one thing that can cause these seals to blow this is having a chain too tight -causes extra stress on the shaft and seal.

[Shorty_925]

You've probably thought of this but one thing that can cause these seals to blow this is having a chain too tight -causes extra stress on the shaft and seal.

Yep been told that and made sure it hasnt been to tight.