750/4 Forgot Cylinder Stud O-rings

sflesch94 wrote:

Warren3200gt wrote:

They are only there as those two stud threads are open to the crank shaft cavity. The remainder are blind. The o rings were there to prevent oil making its way past the stud threads but I've never seen it happen with or without o rings. The open thread end is not below the oil level and only gets oil on it from crank rotation throw off. As that cavity is not high pressure its unlikely to force oil past the thread. 

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That makes sense. So realistically if the oil was getting past the stud threads it would show as oil leakage outside the engine, on top of the head where the head nuts are correct? The base gasket and head gasket should prevent that oil from passing into the cylinder and burning oil? 

No, if oil got past the threads it would show at the base where the stud goes through the bottom fins of the barrel. On 650's the studs don't run in an enclosed tube but are open to the air, apart ftom the outside four.
It's would show as an oil leak in the middle of the engine seeping down onto the crankcase front and/or rear.
The base gasket should stop oil but if it didn't and leaked inwards it wouldn't enter the barrel as it would just drip back into the crankcase off the barrel skirt. 
It wouldn't get as high as the top gasket as previously mentioned. 

The base and head gaskets prevent oil from leaking out of the connections between the three main engine parts.  Oil is forced up into the head to lubricate the cams.  It flows by gravity to the center well where it returns to the sump.  The valve seals prevent oil from running into the combustion chamber.

Knock on wood, even though the O-rings were not installed, there has been no known problems on my bike.  

As mentioned, the O-rings are to protect against oil flowing up around the stud threads, on the studs that penetrate into the crankcase.  These studs have sealer on the threads, so that's one layer of protection.  If, for some reason, oil got past the sealer, oil would find its self in the cylinder passage around the studs in question.  These studs are inboard in the engine, by the cam chain tunnel.   Worst case, there would be a leak, outside the engine, past the base gasket.  Seems unlikely...

Never have or seen a leak without the stud o-rings.
Except you cyl. bank and/or crank case surface looks like a moon crater surface.