Just checked my valves at 25k on my '10 and they are all within spec.
Are people replacing the cover gasket and the o-ring on the side cover?
I have re-used gaskets like this in the past if they aren't damaged.
That said I don't want to dis-assemble the whole bike again if the cover
gasket leaks.

Didn't replace mine and no leaks. If it ain't broke....

There has been some leakage on these gaskets with a small number of bikes.  I also subscribe to the 'If it ain't broke, don't fix it.' philosophy but I don't think I would like to tear the top end down and remove all the plastics and what not to again to replace it.  It's not that expensive, I would replace it.

A leaky valve cover gasket was the motivation for checking/adjusting my valves. In spite of the leak I didn't replace the gasket. Just make sure that when you put it back together that you use some RTV silicone sealer.

Incidentally, I think the reason why my gasket was leaking was because one of the cover hold down bolts was not tight enough. Be careful do not over tighten.

It's better to replace it now, than to find it leaking after you get everything back together.

I believe I've seen mention that '08s tend to leak and an updated gasket is available. Aren't there some o-rings that need replacing too, if the camshafts get pulled?

I just finished my second valve adjust and again re-used the original gasket and I used a thin bead of Permatex Blue RTV on the forward edge. No sign of oil leak before or after. I did the TB sync after the shim swap, doing just enough re-assembly to run the engine. So it was easy to watch for leaks while running the engine for the sync.

Just make sure that when you put it back together that you use some RTV silicone sealer.

Do not use RTV sealant on an O-ring type gasket; it's not designed for it. O-ring type gaskets get installed clean & dry; if there's a leak, replace the gasket.

I believe I've seen mention that '08s tend to leak and an updated gasket is available. Aren't there some o-rings that need replacing too, if the camshafts get pulled?

The 4 oil pipes have   a bunch of o-rings but I did not replace them either. They looked perfect and the oil pipes fit in their whole quite snugly. 

Do not use RTV sealant on an O-ring type gasket; it's not designed for it. O-ring type gaskets get installed clean & dry; if there's a leak, replace the gasket.

Are you referring to the Cylinder Head Cover gasket? I don't consider it an o-ring but it might be made of the same stuff.

Manual Page 5-14:
Cylinder Head Cover Installation •Replace the head cover gasket with a new one. •Apply silicone sealant [A] to the cylinder head as shown.
for those w/o a manual the diagram shows sealant to be applied to the halve moon cut-outs of the cylnder head that mate with the gasket.

for those w/o a manual the diagram shows sealant to be applied to the halve moon cut-outs of the cylnder head that mate with the gasket.

That, I did.

Are you referring to the Cylinder Head Cover gasket? I don't consider it an o-ring but it might be made of the same stuff.

Manual Page 5-14:
Cylinder Head Cover Installation •Replace the head cover gasket with a new one. •Apply silicone sealant [A] to the cylinder head as shown.
for those w/o a manual the diagram shows sealant to be applied to the halve moon cut-outs of the cylnder head that mate with the gasket.

   It's not the material, but the cross-section. The gasket fits into the valve cover with a half-round "protrusion"; that shouldn't get sealant. The cutouts are too "thick" to create a good seal, so they should get a SMALL amount of sealant on the bottoms. The correct sealant is:

Kawasaki Bond (Silicone Sealant): 92104-0004

   This is a grey silicone sealant similar to Yamabond. It is critical that all surfaces are free of oil and grease when using this type of sealant (use A LITTLE carb cleaner on a rag to clean it, then let it dry, then wipe again) Do not use RTV black or RTV blue.

I think the cause of my leaky gasket was a loose bolt. It came that way from the factory. The Kawasaki "quality control legend lives on".

Well so far the Permatex Blue has worked fine for my bikes.

   It's not the material, but the cross-section. The gasket fits into the valve cover with a half-round "protrusion"; that shouldn't get sealant. The cutouts are too "thick" to create a good seal, so they should get a SMALL amount of sealant on the bottoms. The correct sealant is:

Kawasaki Bond (Silicone Sealant): 92104-0004

   This is a grey silicone sealant similar to Yamabond. It is critical that all surfaces are free of oil and grease when using this type of sealant (use A LITTLE carb cleaner on a rag to clean it, then let it dry, then wipe again) Do not use RTV black or RTV blue.

The valve cover does not use a gasket, it is a seal. And because it is a square section rather than an O-ring, it really will not deform with extended use. So in my opinion, it is not necessary to replace it. The same valve cover seal has been used on C-14s since 2008 and there have not been any updates.

Kawasaki specifies a small amount of sealant be used in the radii of the seal where the camshaft bearings were bored in the head. I actually used a small bead of sealant all around the seal, between the valve cover and the seal itself, and when I install the cover I do not fully tighten the cover bolts- I leave them slightly loose (maybe 1/32 of an inch or so). Then after a few hours I tighten the valve cover bolts; this allows the RTV sealant to mostly cure and tends to force the seal to actually seal. C-14s have a bit of a reputation for some oil weepage in the front / left corner of the valve cover and so far the method outlined has worked for me. By the way, I use whatever brand of high temperature RTV sealant I happen to have on hand, and whatever color I happen to have.

The O-ring on the right side crankcase cover can be re-used also but it will tend to flat- spot over time. It is relatively easy to replace though so there is not much risk there even if you have to replace it later. I also use a dab (technical term: it means 'not too much') of RTV sealant where the O-ring crosses the rubber block that feeds the wires to the outside of the cover.

Brian

Just checked my valves at 25k on my '10 and they are all within spec.
Are people replacing the cover gasket and the o-ring on the side cover?
I have re-used gaskets like this in the past if they aren't damaged.
That said I don't want to dis-assemble the whole bike again if the cover
gasket leaks.

Thanks Brian. I will try your procedure today.