No sealer, that is what the gasket does. I have had my head and jug on and off a dozen times as I tried different mods to chamber and ports, mostly on the same head, base and manifold gaskets.
I did have to replace the headgasket as it compressed after 3-4 uses.
If you do put sealer on them, I typically only put it on one side just to hold it in place for assembly, and often that is just contact cement.
If you plan to assemble it once and never take it apart again you can seal it all up but you will curse it if you have to disassemble. One of the best sealers for motorcycle use is ThreeBond sealer:
Yamaha sells a similar product, Yamabond 4:
These are tenacious sealers that are hard to clean up but proven sealers even in applications without gaskets.
If I was satisfied with an engine configuration and was going to ride it across the country, these are what I'd use.
They can be used in all applications, head, base and both manifolds but consider is a final seal.
You will destroy the gaskets taking it apart and the jug will be difficult to remove.
Another type of sealer often used in race engines or things that need frequent disassembly is a filler/release agent, like Graphite spray, aluminum paint or even a silicon spray. I have used all of them. The graphite works best but is dirty, the aluminum paint needs to dry, and the silicon is a release agent only.
Best advice from 40 years of motorcycle, automotive and industrial experience; just use the gaskets and have spares.
Steve
