I'm with JOG, you need to charge a new battery fully before use, it should read about 12.5 -12.7 . the decomp  doesn't work slowly,it either works (moves) or doesn't ,you can adjust it by removing the tank ,the solenoid is on the right side of the frame ,take off the rubber cap in the center, place your finger in the back and push the solenoid out toward you ,the brass shaft should stick out 3 to 5 mm. If you find it's less than 3mm your exhaust valves may be being held open all the time causing low compression. the adjustment nuts are on the bracket on the other side ,above where  the cable hooks to the arm.So you have a stock petcock.the only way you'll get fuel to the carb is in the "prime" position ,unless you replace the vacuum hose. You cleaned the carb ,did you check the float height before replacing the bowl? If the float level is set to low you can have gas in the bowl but not high enough to reach the jets. good luck!