OK, so you cannot explain in detail..
So your talking a vac petcock (I get that from you saying in prime position).
But what about the fuel that's in the carb? You don't think that when not running the fuel won't leak by the needle?
"Yeah that happens to my Z all the time when It's vertical for a while" It would seem that this fella's machine leaks by the needle.
I said School me, not try to fool me.

 

well then he has a problem with his carb. I can wheelie all day long and I can stand my quad up and transport it and it NEVER flooded the carb.
No I cannot explain in detail but I do own 2 Zs and doing a wheelie wont flood them.

 

I don't have any problems with the carbs on my Vinson, my son's Ozark, or my AC 650 TRV, and never had problems with the carbs on my TRX300 or TRX300EX, TRX250R, TRX200SX, LT160, or TRX90...but every single one of them will (did) leak gas if you stand them up on the rear bar and forget to shut off the fuel at the tank.

 

Like you said........"forget to shut off the fuel at the tank". On the Z fuel will not flow from the tank unless it is in the "prime" position. For the record if the carb is full of fuel and the petcock is on "off" (for the bikes that have an off position) and you stand the quad on end, it is likely that some fuel will come out of the overflow or vent hose.

If his quad flooded from doing a wheelie then he has an issue with his carb.

 

The point here is: it -->stalled<-- while vertical. That's when they can flood.
We certainly understand that a carb will not flood while running and doing a wheelie.
A vac petcock is far from foolproof.
""you stand the quad on end, it is likely that some fuel will come out of the overflow or vent hose.""
Yes, and leak into the intake of the motor also.

Hey Tex, go roost spize for me wiill ya...

 

So we are agreement that he has a problem with either his carb or his petcock......if it is operating correctly that wouldn't happen and for sure he will not be getting fuel in the oil.
If you are going to stand your quad up on end for some reason there is a little screw on the bottom of the bowl with a hose attached. You can use that screw to drain your carb. No issues if you petcock is operating properly and you drain the carb.

Go ahead and roost.......I got protection!

dude you just hit 4000 posts!