Vacuum Petcock on 77 KZ650B1

Hey guys, I've read a few posts within threads covering this but I think I have a unique case. I know that the 77 model only came with manual petcocks, and 78+ had vacuum. But, my carbs have vacuum fittings on carb 2 and I think carb 4. If the vacuum fittings are there , does that always mean vacuum is available or is it possible that they aren't drilled through? And, if they are real vacuum fittings, I should be capping these off right? Previous owner just had hoses sticking out of em but not capped.

Reason being I have picked up a replacement vacuum petcock that I'd like to use (I'm aware that the tank may or may not need to be drilled out a bit for the fuel opening).

I do not believe those will be vacuum fittings. They should be ports for vents that will allow the fuel level in the bowls to vary properly. They should have hoses attached to them which then vent to an area under the seat at the carb air filter. In any case they need to vent to open air and not be blocked. See "VENTS" in the first image below. The second image below shows the setup on my 1977 KZ650-C1. If you block them the carbs will not operate properly. Ed

Oh yes! I'm incorrectly referring to the vents as vacuum fittings, you're right. That diagram helps a lot, thank you.

So that won't work, but I could use the vacuum line from a carb boot to operate the vacuum petcock theoretically?

I still use the stock non-vacuum operated petcock on my 1977 KZ650-C1 - no problems after 42 years, so I have no personal experience with the vacuum operated type other than that I've read many, many postings about them having problems with leaky diaphragms.

Having said that, I do think I remember a posting or two where folks hooked up the vacuum line from the petcock to a carb boot vacuum port with some success. Ed