main jets and caps fell out

Huh? How did that happen? I have only ridden the bike (KZ305) 15 miles since the carbs were apart. I took the bowls off and both the main jets and the rubber caps/plugs were laying in the bowl, on both carbs. 

Did I just not tighten the jets enough?

Is there something I can use to replace the caps/plugs? They are unavailable. I can try some rubber rejuvenator but something newer would be better

considering they fell out in both carbs, perhaps they were not given a final tighten for the main jets. For the plugs, oil of wintergreen will soften rubber and even swell the part back to original size. But if too much is used you can over do it. I have no idea if the rubber items its applied too eventually shrinks back down to size or how long that may take. I have used it before and it works great on "restoring" rubber that has hardened but generally in good condition start with. Not sure about new rubber plug availability. Another method may be using something like Permatex brand "Permashield Gasket Dressing and Flange Sealant" applied above the end of the plug that goes into the carb first that may secure it and seal. You'd want a small amount that will not squeeze out visibly anywhere, but covering the circumference of the rubber.

Yeah I probably was afraid to overtighten and undertightened...but I've had the carbs apart many times and they never fell out before.

I have the caps soaking in "rubber restorer" which works great for softening my carb boots. I think with any of those things its a temporary fix.

I was looking at Permashield Gasket Dressing and Flange Sealant as a possible fix but it says it remains tacky...not sure if that's a risk to clog the jets or something? It may be my best option though

I

Maybe use Seal-All. sparingly.  others here have reported using it. the stuff is supposed to be fuel proof.
From the website: "...adheres with superior strength to most substrates and resists gasoline, oil, paint thinner and most solvents."
or search for new plugs. maybe you can find nos on eb or maybe z1enterprises.

Thanks, I'll look into Seal All. OEM caps are definitely unavailable anywhere. I see some Honda caps that might fit the passage, but the OEM's have a long base that is supported by a ridge in the bowl and the Hondas would not reach that far and might pop out. Probably better off with OEM and sealant