O-rings at dowel pins??

[scrambler]

Hey folks,

I`m assembling the top end and being totally confused about these o-rings on the studs and dowel pins. When I pulled the engine apart I had these o-rings on some of the studs, they are still in place. Here`s a picture to illustrate what I`m talking about: 


Now, in the parts diagram we can see a pair of rings on the dowel pins:



See # 11, there should be 8 pieces altogether. 

What are these for? Where do they go? How many of them? If there is a pair shown at one dowel pin/stud, how come there are 8 altogether? 
These rings also show up in the TX500 btw:



Any input is appreciated!
Greg

[jayteenz]

They are a modification to stop oil travelling up the studs and causing an oil leak. There should be 8 o rings in total - 2 for each of the rear studs.

Have a look at service bulletin number 333 which explains their fitment.

[scrambler]

Thanks Jay - This will do it, just googled it, I`ve never come across this particular bulletin or just don`t remember. I`m not sure I completely understand the function though - why only the rear studs and not all?

[jayteenz]

Not sure why myself other than its a TX750 !