Cylinder spigot large "o" rings

[Suzuki_Don]

I know this has been asked before guys. But I can't find the answer any where.

The question is concerning the large "O" rings that go on the bottom of the cylinder spigots before the cylinders are mated to the crankcase. What purpose do these "O" rings perform and is it essential to replace them when refitting the cylinders to the crankcase.

It appears to me that the base gasket would seal everything up OK without the need for these "O" rings.

On another subject: On the 550, the cylinder base gasket has an oval hole where the two rear/outer studs pass through the gasket. An oval "O" ring sits inside this part of the gasket to seal oil passing up to the cylinder head and camshafts.

On the GS650E engine which also uses this oval "O" ring there is no oval cutout in the base gasket to correspond with the "O" ring as is present in the 550 gasket.

Can anyone tell me why there is a difference in the 650 base gasket. It can be seen clearly on the fiches for the two different models.

If the 650 gasket which only has a round hole to fit over the stud is placed over this oval "O" ring is the general consensus that it will work OK and seal the oil being pumped up to the cylinder head.

Comments please -- anyone.

 

[Nessism]

Maybe Suzuki uses a thinner O-ring on the 650 since there is no cut out in the base gasket? Not sure but as long as you are using the factory parts I think you should be fine.

Regarding the cylinder O-rings, I believe they are there to keep oil from wicking up between the sleeve and cylinder though capillary action, and leading to weepage through porosity in the aluminum. The GS1100G doesn't have these O-rings so apparently Suzuki decided at least some models don't need them.

 

[waterman]

I know this has been asked before guys. But I can't find the answer any where.

The question is concerning the large "O" rings that go on the bottom of the cylinder spigots before the cylinders are mated to the crankcase. What purpose do these "O" rings perform and is it essential to replace them when refitting the cylinders to the crankcase.

It appears to me that the base gasket would seal everything up OK without the need for these "O" rings.

On another subject: On the 550, the cylinder base gasket has an oval hole where the two rear/outer studs pass through the gasket. An oval "O" ring sits inside this part of the gasket to seal oil passing up to the cylinder head and camshafts.

On the GS650E engine which also uses this oval "O" ring there is no oval cutout in the base gasket to correspond with the "O" ring as is present in the 550 gasket.

Can anyone tell me why there is a difference in the 650 base gasket. It can be seen clearly on the fiches for the two different models.

If the 650 gasket which only has a round hole to fit over the stud is placed over this oval "O" ring is the general consensus that it will work OK and seal the oil being pumped up to the cylinder head.

Comments please -- anyone.

Sometimes I wish we could talk to the engineers that developed these engines and pick their brains since they may be the only ones that could provide real answers to these tough questions. I am certainly no engineer but my best guess as to differences is that the evolution of the 550 to 650 had proved that it wasn't necessary in the newer (650) design.

It seems that the 650s (E and G) share the same top end components but work with both the plain bearing shaft drive lower end and the preexisting 550 chain drive lower end. I know I am exaggerating with my description of the 550 lower end being the same as the 650E model, but many parts are interchangeable at least from a parts numbers breakdown.

This leads me to believe that the engineers must have realized changing the 650's base gasket to not include the 550's oval cut out would still facilitate adequate oil flow up the stud to the top end. In the shaft drives, oil jets are used in the oval pocket to restrict the flow up the studs. Keep in mind that the 650 shaft drives utilize a higher pressure oil system with plain crank bearings.

By the way, the 650G doesn't use the pear shape o rings around this oval pocket.

These ideas are at best just a guess, I could be way off in my thinking. Just ask my wife, she will tell you the same thing.

 

[Guest]

It was kind of a monkey see, monkey do thing. It keeps oil from going up between thew sleeve and block, but why would that be a problem.

All of the big sleeve blocks we have done over the years have not had any, and no issues.