There should be a gasket here, right?

Yes, and a pretty thick one, like 1/8", so don't get the paper thin gasket material. And no sealer is required but I like to use a small ring on the manifold side, not so much for sealing but so the gasket comes off with it any time it is removed.
 
I didn't run gaskets with my new jbm's and I have no leaks. I did clean my cylinder head spotless first. I def give jbm two thumbs up. I called jbm (sorry, can't remember his name) when they arrived and asked his opinion and he didn't think they would need them, but concurred that they wouldn't hurt if you want to use them.
 
Yes, that's true, but many motorcycle intake tracts are designed with a thick gasket as part of the package to isolate the carb and manifold from engine heat. I don't know for sure that the 650 was designed this way but I'd rather not test the theory myself. On the originals, many times the inner metal housing was showing through the backside so, yes, a gasket was needed. I see the JBMs are all rubber covered on the backside so maybe you could go without the gasket. Still, I would use one.
 
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