flooding cyclinder

[oldman]

I'm stumped, The Valk I was working on was hydrolocking, I pulled the tank and the carbs I checked the petcock, cleaned the tank and replaced the petcock filter. I pulled the carbs and cleaned them (bowls full of sedement) and replaced the float valves. I put everything back together, it cranked and ran perfect. That was a few days ago now it flooding number four when it's running and only when it's running. The carb is not leaking into the intake tube when sitting or for that matter even when it's running unless the tube is bolted to the head. The spark plug is firing when out of the cyclinder, but fowls as soon as it's replaced and the engine is started.
  Has anyone run into this problem? I know I'm going to have to pull the carbs back off but sure would like some input on what the problem might be before I start going back thru everything..
  Any insight would be greatly appreciated, thanks..

[Pete]

Based on your description, it only floods when air is flowing thru the carb.
The air picks up gas but to much.

Would seem to indicate jet, needle or emulsion tube issue.

Example jet not tightened and falls out into the bowl or same with slow jet (emulsion tube).
Or pilot in-correct install or adjustment, Check the placement of the oring, washer and spring.
Make sure there is not 2 of anything especially orings or washers. Look close as they will hang in the passage. 

[Valkpilot]

I pulled the carbs and cleaned them (bowls full of sedement)

This implies a bad screen in the tank.  If so, is it possible that the number 4 float has already picked up a piece of junk and become stuck?

[Rocketman]

If it's flooding while it's running, either there's a problem with your jets, or it's got a massive leak in the needle seat.  If it's the needle seat, and since it's not leaking when stopped, that tells you your petcock is good.  (one bright ray of hope, at least...)

[Pete]

Addendum to my previous post

Float valve set to high or mal-functioning allowing to much gas in the bowl.

[oldman]

Thanks for all the help, when I tore it back down I found the culprit, my carelessness in retightening the idle jets after cleaning them was the problem. Number four idle jet was only started by finger and had not been properly tightened and as a result had vibrated back out. needless to say I went back and rechecked the rest. Thanks again for all the help..