1978 KZ650 B2 Carb filling problem

Hi all,
I just replaced the petcock on my bike because it was leaking and I changed it to a manual from vacuum. Did not bother w/ the rebuild kit. Anyhow it seemed to work fine but I took it out on a short run about a mile and a half. It started to bog down when I gave it gas and eventually died out. The carbs ran dry. I waited about 5 minutes for them to refill and she fired right up. What the heck is going on? I have not a clue as to what could be the problem. Any info would be greatly appreciated. Thanks,
Sean

I'd check the fuel flow to the carbs and see if a vent line or two is blocked. Check the gas tank vent hole(a small hole near the gas cap)if it's blocked the fuel won't flow properly.

EL Architecto wrote:

Hi all,
I just replaced the petcock on my bike because it was leaking and I changed it to a manual from vacuum. Did not bother w/ the rebuild kit. Anyhow it seemed to work fine but I took it out on a short run about a mile and a half. It started to bog down when I gave it gas and eventually died out. The carbs ran dry. I waited about 5 minutes for them to refill and she fired right up. What the heck is going on? I have not a clue as to what could be the problem. Any info would be greatly appreciated. Thanks,
Sean

Hello, Sean, and WELCOME to KZR forum!
We're glad you're here!

If not already done, would test run with the fuel tank cap left ajar (not snapped closed). This assures more than ample venting for test purposes. Of course, be certain there's enough fuel in the tank.

Where same suspected fuel starvation problem persists in spite of adequate venting, perhaps crud or grit suspended in the fuel is hovering about and collecting onto the petcock pick-up tubes inside the tank, and thereby obstructing fuel flow into the petcock. Could remove the tank and flush it out with clean gas to remove any loose grit and crud.

Or maybe the round screen petcock filter is clogged. The screen filter is located atop the removeable petcock sediment cup. Be sure to turn the petcock to OFF position before removing the sediment cup.

Sometimes an in-line fuel filter gets clogged up and fails to allow sufficient fuel flow.

Objective is to have ample fuel exiting from the in-line filter.

Good Luck!

Thanks guys, turns out the vent hole was plugged with crud. I cleaned it out and runs perfect. Thanks for the ideas.
Sean