Center Seal

[Justgotit]

  I just re-read " Crank seals for dummies". It doesn't mention the center seal. Is it not necessary to change it as often as the others?  I always thought that it was the thing to do. Or do you need to completely dis-assemble the motor for that?

[Trucker]

The center seal would be very rare to need to be replaced. The orings on the seal can be easily replaced if needed.

[jimvw57]

The center seal is what they call a 'Labrynth seal' which uses a series of oil passages to seal the motor. It uses the oil injection pump to do this so keep that oil tank full. As such, there isn't much to wear out.

 If you feel the need to replace it, the crankshaft needs to be pulled apart, replace the seal, and have the crankshaft pressed back into place.  Intruders and air cooled motors use a regular center seal and since they are inside the crankcase, they are pretty protected from the elements.

When someone decides to remove the oil injection for racing, or just because they don't want it, On the invaders it is necessary to change the crankshaft to an Intruder crank, or leave the oil pump in lace and feed only the center seal.

[mswyka]

I have quite a bit of respect for Jim, but in this case I will go on record as disagreeing with the prior center seal assessment.  The grooves in the center seal trap the compression wave keeping it from transferring from one cylinder to the next while the engine is running.  This is why the engine transfers fuel to the cylinder when running but will not pass a cylinder to cylinder pressure test.

The oil injection on the Invaders is distributed to the bearings and is considered to be necessary because of the bearing shields that were used on the Invader cranks.  The center seal is not sealed by oil and Invaders and Intruders use the same center seal.  There should never be a need to do anything with the center seal other than perhaps replacing the "O" rings that are visible on the outside if they become damaged.  Somewhere around here I have a center seal photo or, if I can't find that one I will take a new one for you.

And Jim, I do say this with all due respect.

[jimvw57]

Entirely possible I have it wrong, but that was how it was explained to me. I don't claim to know everything and I always appreciate the words of someone who has better information than what I got.

[gixxer6]

This has been discussed before:  http://kawasakitrax.com/kawiforum/index.php?topic=252.msg1371#msg1371

[kawhead]

the oil that is trapped in the groves of the center seal keep the cyl pressures seperate, most 2 cyls use a version of this.... and the shields are the diff. between vader/truder cranks.

[Justgotit]

   Thanks for all the feedback. That's why this is such a great site. Ideas and facts. This is the 4th Invader I've had and I've had good luck with 2 of them. Not such good luck with the other. This one is nice so I am going to make it like new. After all, all it takes is time and money and good information. Thanks again to everyone who replied.