My 1973 CB175 has an issue where it runs fine for about 3/4 mile then starts to stall. Ive only had it for a few weeks and it’s been doing this since I’ve had it. I’ve cleaned the carbs and and set the floats At 21mm. If I let the fuel run for a minute and then pull the carb bowls, the fuel is about one half inch from the top which seems about right. I’ve ve adjusted the valves and set the timing but I still think its a fuel issue. After I pull over and wait 30 seconds, it runs fine for a while and starts to stall again. The fuel cap is venting okay. I’ve tried running it without the fuel cap with the same results. It had fuel filters but I removed them as the tank is spotless. I installed new fuel lines. As I was pulling the tank the other day, I was draining the fuel Into a can and noticed only the left side of the petcock was draining fuel. If I stopped the left side up then the right side started draining. Then if I stop up the right side, the left starts flowing again. I had previously removed and cleaned the petcock and blew it out with compressed air and everything seemed fine. Could I have damaged something? Is this normal? I’ve also replaced the battery and the rectifier and cleaned all the wiring connections. Thanks for any advice.