top end O rings

[Rota Ash]

O rings, hey do any of you guys use general o rings from an O ring shop rather then ones from your dealer, are the factory ones from your top end just made of nitrile or are the viton, coming from a rotary backgroung and i know there is pretty big savings in using the off the shelf stuff rather then genuine parts 

[MXLord327]

Good question!!  I have always used the OEM Yamaha o-rings, but this would be good to know!!

[Rota Ash]

this is taken from a rotary thread :

as long as the substitutes you use are viton or nitrile ( in some cases )
then you are using two rubber compounds that are very resistant to oil and most fuels
and are also more stable than most with temperature

- nitrile and viton both have an Achilles heal
viton is not as stable as liked in presence of aromatic based solvents ( specifically ketones )
nitrile is not as stable in heat as viton , and doesn't like ester acids
and when formulated to be resistant, can loose its flexibility
( at any rate the two remain the better of the resistant rubbers )

the other O rings used by mazda throughout the motor appear conventional butyl nitrile
of which the viton could actually be considered a superior upgrade
( though most O rings sold in kits are likely nitrile )
viton is , by definition , a flouro- rubber
O-rings made of viton are typically color coded as black
its 200 c stable
and proves to be more flexible than nitrile when specifically formulated to be heavily solvent resistant

mazda choose to flourosilicon coat on the early green type oil control ring
( the simple cheaper black one appears nitrile, but may be possibly be viton , but is not coated )
mazda have used the flourosilicon coat onto the nitrile
to provide a protection for the rubber for its known weakness

[Rota Ash]

here is a pic of my 02 RM250 top end, the outer ring is black, i would say its just a simple 50 cent, nitrile O ring due to the fact it only comes in contact with coolant and will most likely never see above 100 degrees C. the inner ring is green which is a coated nitrile, you can still easily buy these from an o ring shop or even put a viton ring there in it's place which is actually a better then the genuine part and should cost you all up around 3.50 max, the only thing is the size, i am rebuilding my 2002 RM 250 and my mate is just about to pull his 2001 RM 250 apart, i have already bought the genuine O ring's for my bike but will prob give them to him and use the general ones for my bike just to see the difference for comparisons sake 

[admiral]

i've never found exact replacement O-rings from aftermarket sources. they always seem to be too thick, too thin, or the diameter of the ring not quite right. heck even some aftermarket gasket kits like Cometic come with O-rings that are a little small.

[Rota Ash]

ok got a price for the o'rings from my local supplier and it is about $10 cheaper than the factory parts, the seals are slightly thicker but will sit in the groove actually better, and are also made out of viton rather then nitrile, the green inner ring isn't a coated ring at all just a standard coloured nitrile ring, i didn't get a price on the cheaper nitrile o'rings because they didn't make them in that size, gonna try and get a discount there from a mate with an account with them then they will cost me fark all , so basically it's a win win situation, there cheaper and better