A friend of mine has so far done a good job of rebuilding the motor on my old 83'. The bike starts and runs great but kills when throttle is applied. He says it feels like it is starving for fuel and is not flooding. He went through the carbs completely and still has the same problem. The bike ran OK before rebuild. Could this be a timing or valve issue ? Timing chain too old/stretched maybe ? Looking for suggestions. Thanks for the help.