Popping/Dies after warm up

I put the fuel tank on yesterday and got the bike to fire up. Had to use a little starter fluid but it fired quickly with out any troubles. Bike idles and responds wonderfully cold. Once bike is warmed up and I can hear idle come down just a tad it runs for about 10 seconds then dies. After this, it is about impossible to start up again. I did check my external fuel shut off right after the petcock and it is clean and open, but I did notice that the fuel running through line has quite a few bubbles in it and it seems to be moving very fast. I am stumped, everyone I talk to says clean the carbs, but for some reason I think was it warms up the fuel flow can not keep up. I have been running straight out of header, no muffler. I do notice that it runs worse when I put the muffler on vs leaving it off. I did replace the Generator cover with one from a 83 KZ750 L3 which had a 2 wire, but I put the 3 wire that I had in the case. When I detached the 3 wires, they were not color coded so I assume that it does not matter which ones get plugged where. Any ideas?

The guy that I bought bike from was the kind of guy who buys bikes super cheap and gets them running well and makes a tad bit profit (60 year old guy AWESOME DUDE). I rode bike home 65 miles with ZERO issues. But since tear down I have not touched carbs at all, which would make me think its not the carbs.

Let the thinking begin....lol :ohmy:

did you already get the new tank or using the old tank?

Using old tank. But they fixed the leak. I did take apart the petcock, replaced the seal inside there. Everything looks nice and flows well. I just dont understand how it can run so so so so well for about 5 mins until its warmed up, idle kicks down, idles for about 10-15 seconds then dies. Once that idle kicks down, if I hit throttle it will die instantly.

Could be a number of things. But from what you described it may be your pilot circuit may be clogged. Do you have a gravity inline fuel filter to keep an debris from the tank from reaching the carbs? If you think it has something to to with fuel delivery, you can make a temporary small fuel tank and hang it at a higher level than the carbs. Could even use a funnel going into a hose but have to worry about spilling fuel everywhere. Could also be float levels. But since you didn't touch the carbs, what kind of set up did the bike have before with regards to air filtration and exhaust?

The previous setup on bike was Uni Pods and Vance and Hines 4 into 1 exhaust. I switched to Mac exhaust with 4 silver open pods. Nothing too much different. Yes it does have a gravity filter. It looks clean.

You said it is impossible to start once its warm and dies. Maybe its heat related and electrically orientated. You can eliminate this possibility by trying starting fluid after it dies and doesn't want to start. If it starts with starting fluid for a few seconds, then you at least know its not electrical. If it doesn't then I would start checking your ignition system.

Been tinkering for past couple of hours. Drained fuel in tank. Went to gas station and for fuel. Bought a can of sea foam. Dumped in. Started up and let bike idle for awhile. Turned choke off. GOOD TOO GO! Had some slight hesitation here and there but sounds good. Pulled the baffle out of my old exhaust. Does anyone know where to get something similiar. The mac baffle is pitiful design... Yes that thing is nasty!!

s1170.photobucket.com/albums/r532/Marklo...=20130119_215725.mp4

Not surr if this will work but here is a short video of bike running. Noticed an exhaust leak around header. Quickly once bike warms up it goes away. Should I be concerned? Mac makes a crappy header...never fit truly right thats for sure....

with a new header and gaskets you will have to keep tightening the nut for a while after a few rides before they seat good. i had to tighten mine a few times after i rode it to get rid of any exhaust leaks.