kz400 dies after 30 min

Hi guys. New here. Have a question about my kz400. It will start to miss and will die after about 30 minutes of riding and won't restart until cold. I've replaced the points and rejetted the carbs for pod filters and opened up the exhaust. Bike runs great for the first 30 minutes. Just replaced the coil with one off a z1r to see if it changed anything. Still did it but I got home before I was stranded. What do you think this could be? Also should there be bubbles in my oil window when running?

1. Are you sure that your new ignition coil has the correct resistance for your bike's ignition system?

2. Does your fuel filter have a paper filter media or is it designed for a pressurised (fuel pump) system? Such filters can greatly reduce or even stop the flow of fuel in a gravity feed system.

3. I'd be mildly concerned about bubbles in the sight glass. Are you sure the oil has not been contaminated? Are you sure it is top-notch motorcycle oil?

Yeah the coil is the correct resistance. I have 3 coils. The original. A z1r coil and a new coil. I'm pretty sure they are all 3.5 ohm coils. I use a visible type filter with a screen in it. Working on the bike right now and it won't even start. I hate wiring. The oil is Mobil 1 4 cycle motorcycle oil 10w40.

Could the battery have a dead cell?

Doubtful it's pretty much brand new and putting out the proper voltage

Have you adjusted the valves and made sure the mixture is correct after your mods?

Mixture is perfect, brand new 3 angle valve job to go with the whole engine being rebuilt. Split the cases and replaced the timing chain, guides, rings, bearings, oil sumo screen, oil pump, etc etc. Had a very reputable old school shop do the head for me. Decked it, cleaned it and did the valves, New Springs, retainers, and recut the valves and seats.