I have an 88 LT230E. It will run about two minutes backfire and stall and will not start for like five minutes. I have done the usua. FIrst I replaced the coil and the spark plug. Still the same thing. Checked spark as soon as engine dies and it has a good hot spark. Next up I adjusted the valve lash as I am certain it has never been done. Same problem. Removed carb and ultrasonic cleaned the carb and rebuilt it with all new jets. Set the mixture screw right back where it was and I am still getting the same problem. Removed the fuel valve and it was perfect. This thing has me scratching my head. Any ideas?