TOPIC:

You're right in that these carbs have no overflow tube, and it's not the greatest design feature. Because of this, it's ALWAYS good practice to shut the petcock off whenever you park.

Hydro lock ain't fun.

I think the only reason that I escaped a hydrolock tragedy when I had my "crankcase full of gasoline" event was because it happened in the winter. The bike had been sitting for several weeks, so the gas had time to leak past the rings . . .

Check your "wet" levels !
Your restart problem is VERY reminiscent of the exact same issue I started having many years ago.
If it starts initially and then only with starter fluid (VERBOTEN) or after it sits 15 minutes then it's NOT "ignition" or "electrical".
The oversimplified explanation is simple: When you first start, it's "DRY", so it starts on what Fuel is sucked in from the idle circuit. Then you ride it, stop, and it won't restart. That's due to it already being "WET" from running PLUS your fuel level in the bowl is too high. It's flooding. OR it's experiencing a "flooding-like" condition. Waiting 15 minutes lets everything dry-out enough to be back in an ignitable mixture ratio. Starter fluid starts it because it's so much more volatile therefore easy to ignite regardless of the WET condition.

If the needle-valves are working correctly then your floats may be questionable.

Check your "wet" levels !

I think you're right -- it's always "felt" like flooding to me. Since this is a relatively new development not long after a professional tuneup, I'm hoping it's just a stuck float that's causing the problem. I'm trying to avoid paying someone to pull the carbs off just to check the fuel level in the bowls. Can't do a "wet" check from the outside -- my carbs have no overflow tubes. So I might drop the bowls with the carbs still on the bike, and feel with my to see if the floats feel "free."

touringguy -- Just wondering: How long have you owned a 1300 ?

I've had this KZ1300 for about nine months, but I've owned 30-40 (I've lost count) of Japanese motorcycles over the past 45 years.

Why do you ask?